But is Islam just in its laws that Muhammad himself practiced and invented?
This article says no for ten verifiable reasons.
Here are four points you must read, before reading this article:
First, sometimes these ten points quote the Quran or omit it; sometimes they quote the hadith (reports of Muhammad’s words and actions outside of the Quran) or omit it. This is done only to keep down the length of the article. No one should be fooled into believing that these harsh and excessive laws were invented in the fevered imagination of extremists who came long after Muhammad. These harsh and excessive laws come directly from the founder of Islam in his Quran and in his example in the hadith.
Second, each of these ten reasons has a back—up article (or more) that is long and well documented with quotations and references to the Quran, the hadith, and classical legal opinions. The supporting articles also examine the historical and literary context of each Quranic verse. If the readers, especially critics, wish to challenge one or all of these ten reasons, or if they simply doubt them, they should click on the supporting articles. They will see that Muhammad himself actually laid down these excessive punishments and policies.
Third, it must be pointed out that these harsh laws are not (or should not be) imposed outside of an Islamic court of law. Careful legal hurdles must be passed before the punishments are carried out. However, even in that case, it will become clear to anyone who thinks clearly that these punishments and policies are excessive by their very nature, and excess is never just, as Aristotle taught us in his Nicomachean Ethics.