Why have atheists become so evangelical?

OK, so if you don't believe in God or an afterlife, why are you so concerned about the beliefs of Christians, Jews, Muslims, etc.? Why don't you just enjoy your life and let others fend for themselves? You call Christians and other religious people so ignorant and stupid, but why do you care if we are stupid? If you are enlightened, why bother with enlightening us, since you believe that we are all gonna die and our knowledge of existence will cease to exist?