It's hard to kill an idea, but easier to kill yourself. Religion CAN (if you take it seriously) make you hugely guilty, and lead you to the most outrageous ends to 'deal' with it. Over time I believe it can mentally effect you in a negative way because of this really negative view you can have of yourself.
I think certain aspects of religion; the ethics especially, can be of great value. However, it goes too far when you can't be comfortable with who you are;even with your family or friends, because the bible 'condemns' you for it, even if it causes no harm to anyone.