Believing in something

Why do some people spend so much energy complaining about things they don't believe in, and trying to convince other people not to believe in it either? Why don't they spend this energy finding something they can believe in? Or why do they pick one little aspect of something and decide, because they disagree with that one thing everything must be wrong? Of course I know the answers to all these questions but I just don't understand why people act so illogically. I for one don't believe in Buddhism but I don't spend all my time researching more things about Buddhism that make me not believe in it (actually Buddhism has some really good things about it). I just want people to respect one another and their beliefs, is that ever going to happen?