Why are most atheists on the internet so obnoxious?

In real life, 90% of my friends are atheists and they are extremely tolerant of theists. The Internet just seems to slap a label on you of being stupid/ignorant if you believe in God

And I've noticed that most of the hate is directed to Christians in particular.
I'm not saying all atheists on the internet are rude. But the large majority of them are just extremely harsh on having a faith in God.