It is easy to see why this won't work. If we are trying to evaluate the results of an actual religion, in the actual world, then we cannot automatically put everything good into the religious category, and chalk up everything evil to non-religion.
The second, a remarkably stupid one propagated by Karen Armstrong, is that religious wars of the Middle Ages weren't really religious, because there was not separation at the time between religious and secular realms. Everything was religious.
First of all, there is the whole business about religion before the modern period never having been considered a separate activity but infusing and cohering with all other activities, including state-building, politics and warfare. Religion was part of state-building, and a lot of the violence of our world is the violence of the state.This is true, but the implications are the opposite of those drawn by Armstrong. It is precisely the implication of religion in state violence and non-state terrorism that is at issue, after all, for those in search of secular alternatives.
This idea goes hand in hand with the first. Religion itself is pure, so even when it is implicated in one cohesive political war-machine, it retains its purity, somehow.
The third is that religions do not truly preach the horrible things they do preach. Everything unacceptable becomes irrelevant or metaphorical, and people who actually believe that holy books say what they seem to say are naive fundamentalists. Since religion is pure and beyond critique, those who act on what the books actually say are not truly religious. Only the moderate, intellectual type are truly religious. Those who don't actually believe in anything very firmly.