This sounds like a good point. But lets examine what Islam is. Can Islam be Islam without the Quran or the Hadiths?
If Islam can be Islam without the Quran and the Hadiths, then who decides what the rules of Islam are? Can anybody say that he follows Islam, and make up his own rules? If the Quran and the Hadiths are not the foundations of Islam, where are the rules that separate Islam from any other religion?
On the other hand, if the Quran and the Hadiths ARE the foundational writings of Islam, how is it that people can say that Muslim terrorists are not part of Islam? After all, there is terrorism type violence written right in the Quran and the Hadiths.
If someone says that such violence writings are only in self defense, that's not what the Quran and the Hadiths say. Even the traditions of Islam say that the writings of the Quran and the Hadiths refer to terrorism violence. To say that they do not, is to change the meanings of Arab words as well as Arab history.
If you are a Muslim, and you want to be peaceful towards people of other religions ALL THE TIME, you have to be a very weak Muslim. If you want to be a strong Muslim, and follow what the words of the Quran and the Hadiths say, rather than follow what you want the words to mean, then you have to be a terrorist.