I am not exactly on board with your summation there.
Christianity and Judaism will always have misguided extremism found within its ranks because people are affected by many elements. Which includes the devil, pride and their own passions and weaknesses. It can also bring on mental instability. However, I contend that is a very small minority in Christianity, Judaism, most other major creeds and even in the large body of non-believers.
It is in Islam where something else is taking place, IMO. ISIS is but one band of many bands or circles of extremism in Islam. Islam has never been at peace with those who do not believe as they do. Islam has always spread its faith and influence by the sword. Islam has no empirical evidence to demonstrate it is from God. Islam has so many violent murderous followers it cannot be from God. Islam cannot be the one true religion and then its God allow for millions to become corrupt and evil because of it. If this discussion were expanded upon it could be demonstrated all the more easily, but enough said.