It's a belief for people to hold onto, as opposed to something like 'The world is small, nasty, complicated and everyone dies alone'. I'm not sure about the common sense of people who follow religion, but it gives them some hope, something to build their dreams around.
As for taking action against religion, I've seen it happen, and I'd wager you have as well. Back in Soviet Russia they outlawed religion, tried to anyway, and more recently we have seen the intolerance of Islam, and sorry to bring this up but Muslim extremists have spoken of their intolerance for other religion. I'm sure Christianity, Jusism, ect do so as well but we've seen it in their voice and we've seen it in their acts, and there are those who believe it is their right to persecute those who follow religion, to take away their beliefs.