Gerard's post about Agnostics pretty much summed it up for me. I definitely agree, I don't believe that there is an almighty God, but I'm not stupid enough to say I know everything about everything, because I don't.
I've stated this here before: I do have my certain beliefs, but I also have my doubts.
You can't just change somebody's beliefs in a second. Beliefs are one's own opinion, and you shouldn't have to change your beliefs just because someone says "OMFGZZZRELIGIONISFUCKEDINTHEHEADCOMEJOINMEANDMYFELLOWHATERSLOLOLOL!!!"
Religion is one way for people to feel good. One of my close friends became a Christian after she was going through a really rough patch in her life, and she's become a better person because of it. Religion and beliefs give people something to believe in. But when others start to bash the religion in question, they're likely to get upset with you because that religion may have done good things for them.
@Connor: You're obviously pretty firm with your atheist stance, but really. Everybody has their own views.