Why are _some_ religious people so quick to condemn (judge) others?

I have been told more than once that I'm going to hell for being who I am. I have seen others say that my religion is a false religion and then, in later comments, demonstrate their ignorance of my beliefs. I can understand the apostates (those who have left the religion for whatever reason and hating it and what it stands for), but for those who are supposedly religions preachers, who claim to be Christian, I am at a total loss. Can anyone enlighten me?