Both of those are incorrect. There were more than religious reasons behind the Christian Crusades and 9/11, or terrorist attacks in general. There are disputes over territory, disputes over who should have what resource, who is the superior culture, etc. Getting rid of the concept of God isn't going to do jack diddly squat to stop people from killing each other and being stupid. If you truly believe that religion is the world's scourge, then I'm sorry, but you clearly massively underestimate Human stupidity.