That's an interesting point of view, I'm assuming your argument is based on original scriptures or old doctrine. But at what point does an old religion cease to be what it was, and evolves into an entirely different entity? If you are arguing that Islam has been corrupted by so many of its adherents not following the original tenets, then when does one just say, "this is modern Islam; it has changed." I would argue that solely based on history of conversion through warfare, but that is a different discourse. All religions eventually become corrupted over time and cease to be what they once were. If you look at Christianity it has changed multiple times (for good or ill), and is in a constant state of reform. I sympathize that you feel bad for Muslims around the world, but right now this is Islam. If it is truly based on teachings of peace, then it is time for reform.
It is NOT a teaching of peace, nor is it a teaching of violence. It is a book meant for guidance in every sector of the human life, human event, and human being (as in, from dawn to existence). When Islam was revealed to the Prophet Muhammad, the ME was in a state of bedlam with idolship rampant among other things. War soon broke out after that and the contract of war was taught to Muhammad (i.e what he should do, peace treatings, torture, all of that).
The Qur'an is as much of a law book as it is a religious scripture. Everything in the Qur'an is absolute and cannot be overtaken by ANYTHING. You say that other religions have changed due to external circumstances which is absolutely true. Some change has been for better, some change for worse.
The worse change though is when it comes at the hands of individuals who believe they can make sense of something that literally cannot be mastered, perfected, nor discovered (in its fully capacity). Imams and scholars have diluted Qur'anic teachings by injecting their own culture within the DNA of Islam and by following Hadith (what followers of the prophet Muhammad "heard" him say or "believe" is right due to the fact they lived in those (relative) times.
Islam does not have to adapt. You literally cannot change the text of the book without corrupting it entirely. It is Muslims who have to adapt and push aside ancient views and beliefs to better fit in the more liberal and democratic world we live in today. Of course, with the way the ME is now, that will probably never happen.
