The most poisonous parasite that exists within man is fear. Religious fanatics have the most doubt of all and translates into the most fear. That is why they have to fight so hard and be so dogmatic. Otherwise the doubt might creep back in and destroy their ideology which they hold on to with all their "heart." Their ideology is all they have. They have no personal identity without it. Everything is wrapped up in the cause. Without that, they have nothing.
Religion has done a lot of damage in some instances, however, the vast majority of wars and instances of genocide have not been related to religion. It's a fallacy to suggest that most of humanity's problems stem from religion. Money, culture, and politics are what have caused most of the problems the directly affect "civilization." Some people just let their attitudes towards religion affect their intelligence and judgement. More education, less propaganda.
I'm of the opinion that religion doesn't do anything that people didn't want to do in the first place. Religion is just words on paper. They only have the power that we give them. They only do the damage that we let them. So the problem doesn't come from religion at all. It comes from people and their fear and dysfunction. And you don't have to be religious to be dysfunctional.