There are a lot of differences among people who follow Islam themselves. Shias and Sunnis often say that the others are not 'real Muslims'. Ahmadiyas are Muslims who believe that Muhammad was not the final Prophet. They are treated as non-Muslims in Pakistan since they do not believe in the finality of Muhammad's Prophethood. The basis of the Shia-Sunni divide was actually succession to Muhammad. After Muhammad, his friend and close aid Abu Bakr became the Caliph, but some of Muhammad's kin felt that they had the claim to the Caliph's throne.
There are many things which are very clear but interpreted differently. For example, according to Islam, apostates are to be given death penalty. But then there are many others who try to interpret this differently. The encyclopedia wikipedia on Apostasy in Islam reports : "The Quran itself does not prescribe any earthly punishment for apostasy; Islamic scholarship differs on its punishment, ranging from execution – on an interpretation of certain hadiths – to no punishment at all as long as they "do not work against the Muslim society or nation." According to Islamic law apostasy is identified by a list of actions such as conversion to another religion, denying the existence of God, rejecting the prophets, mocking God or the prophets, idol worship, rejecting the sharia, or permitting behavior that is forbidden by the sharia, such as adultery. "
Would God who made Islam as his only true religion leave so much ambiguity and difference of opinion among followers of his own true religion about a thing so important as apostasy? Apostates are given death penalty is many places. This is the legal provision in many Muslim countries even today, like Afghanistan a state supposedly rescued by liberals from the radical Taliban, which gives death penalty for leaving Islam and of course Saudi Arabia where there are laws to punish people for sorcery in today's 21st century! If there is no compulsion in religion and God can easily make all humans as believers then why should apostates be given death penalty?The Quran in 2:27, 2:39, 3:90-91, 4:89, 9:66, 9:74, 47:25-26 makes it clear that apostates are to be punished. Let us see what it says:
"Those who break the covenant of Allah after ratifying it, and sever that which Allah ordered to be joined, and (who) make mischief in the earth: Those are they who are the losers. How disbelieve ye in Allah when ye were dead and He gave life to you! Then He will give you death, then life again, and then unto Him ye will return. " (Quran 2:27-28)
"They long that ye should disbelieve even as they disbelieve, that ye may be upon a level (with them). So choose not friends from them till they forsake their homes in the way of Allah; if they turn back (to enmity) then take them and kill them wherever ye find them, and choose no friend nor helper from among them". (Quran 4:89)
"They swear by Allah that they said nothing (wrong), yet they did say the word of disbelief, and did disbelieve after their Surrender (to Allah). And they purposed that which they could not attain, and they sought revenge only that Allah by His messenger should enrich them of His bounty. If they repent it will be better for them; and if they turn away, Allah will afflict them with a painful doom in the world and the Hereafter, and they have no protecting friend nor helper in the earth. " (Quran 9:74)
Let us see wikipedia again:
"In medieval times, several Sunni schools of Islamic jurisprudence held that apostasy by a male Muslim is punishable by death, differing on whether to execute the apostate immediately or grant the apostate an initial opportunity to repent and thus avoid penalty. They also differentiated between harmful and harmless apostasy (also known as major and minor apostasy) in accepting repentance. However, other scholars also held different views, such as that of Ibrahim al-Nakha'i (d. 715) and Sufyan al-Thawri and their followers, who rejected the death penalty and prescribed indefinite imprisonment until repentance. The hanafi jurist Sarakhsi also called for different punishments between the non-seditious religious apostasy and that of seditious and political nature, or high treason.
Medieval Islamic scholars also differed on the punishment of a female apostate: death, enslavement, or imprisonment until repentance. Abu Hanifa and his followers refused the death penalty for female apostates, supporting imprisonment until they re-embrace Islam. Hanafi scholars maintain that a female apostate should not be killed because it was forbidden to kill women by the Islamic prophet Muhammad, and because women are unlikely to take up arms and endanger the community.
According to Wael Hallaq apostasy laws are not derived from the Qur'an. In modern times, some Islamic scholars oppose any penalty for apostasy, including Gamal Al-Banna, Taha Jabir Alalwani, and Shabir Ally. Quran Alone Muslims do not support the apostasy penalty, citing verses from Qur'an which advocate free will.
Others believe that the death penalty can only be applied when apostasy is coupled with attempts to "harm" the Muslim community, rejecting the death penalty in other cases. These include, Ahmad Shafaat, Jamal Badawi, Yusuf Estes, Javed Ahmad Ghamidi, and Maliki jurist Abu al-Walid al-Baji.
However, Zakir Naik stated that if a former Muslim speaks against Islam then that is considered as treason and punishable by death in a country ruled by Islamic law, he also stated that he does not know of any country which is ruled by 100% Islamic law., a view which is held by other contemporary Islamic scholars such as Bilal Philips, and Yusuf al-Qaradawi, the latter reduces the punishment to imprisonment till repentance in the case of an apostate who did not proclaim apostasy, whereas the judgement which is still widely adopted advocates death for every ex-Muslim, for instance, Sheik Muhammad Al-Munajid the owner, writer and administrator for the popular islam-qa.com site advocates that judgement stating that leaving them alive "may encourage others to forsake the truth".
Contemporary reform Muslims such as Quran Alone intellectuals Ahmed Subhy Mansour, Edip Yuksel, and Mohammed Shahrour have suffered from accusations of apostasy and demands to execute them, issued by Islamic clerics such as Mahmoud Ashur, Mustafa Al-Shak'a, Mohammed Ra'fat Othman and Yusif Al-Badri.
Prominent recent examples of writers and activists killed because of apostasy claims include Mahmoud Mohammed Taha, Faraj Foda, Rashad Khalifa, Ghorban Tourani, Necati Aydin, Uğur Yüksel, and the Egyptian Nobel prize winner Najib Mahfouz was injured in an attempted assassination, disabling him until his death in 2006.
The case of Abdul Rahman, an Afghan who converted from Islam to Christianity, sparked debate on the issue. While he initially faced the death penalty, he was eventually released as he was deemed mentally unfit to stand trial."
Naturally, how can God leave matters so ambiguous in such a crucial thing? Even a cursory reading of wikipedia page on apostasy shows the massive difference of opinion on the subject. In some countries like Malaysia, permission has to be obtained by a Muslim for becoming an apostate. An article on Shia-Sunni divide on wikipedia is here. Would a true God leave so many differences among followers of his religion? He would have made the Quran clear and simple and left no doubt in anyone's mind on all issues. As a minimum, God can come today, show himself to the rest of the world, or at least send angels on earth to reveal to all Muslims which is the correct form of Islam.
There are also various differences of opinion on issues such as photography being allowed or banned in Islam (Taliban interpreted it as 'total ban' on photography banning television, cameras, photos). If this is wrong and Islam does allow photography and TV, then why would God give Islamic scriptures in a manner whereby followers of his 'only true religion' who most genuinely are devoted to his religion and genuinely believe that what they are doing is right and as per God's command misunderstand Islam and ban TV and internet and take Afghanistan back to the 7th century? Or if photography is indeed banned, then why do most Muslim nations allow TV? And then there are issues like wearing veils for women in Islam, men growing beards (whether necessary or not), whether there should be a minimum age for marriage in Muslim countries. Many Muslims who have supported 14 as the age for marriage for girls (which is also very low, it should be at least 16 if not 18 as in India) and those Muslims who have demanded this have been called as 'apostates' by others. God could have simply clarified in the Quran and given precise details of what he wanted, how he wanted laws to be applied.
There are many who genuinely believe that Taliban interpretation of Islam is wrong and that terrorists who killed innocents in the name of Islam and God are not true Muslims. These Muslims who genuinely believe that Islam is a religion of peace believe that Islam is true and is from God, Muhammad was His best and last prophet. The Taliban which is completely different in ideology and practice also genuinely believes what it does and believes that Islam is true and from God and that Muhammad was His best and last Prophet. If this is the case, why would God make a religion in a manner where his genuine followers interpret things differently? God can today send angels and correct one of the two different ideologies which must be wrong- i.e. either Taliban or the people who genuinely believe that Islam is a religion of peace.