Things people are overly hostile about on the internet
 

Grammar

The Existence of God

Creationism/Evolution

Organized Religion

(the last 3 often get put into one, but I think they are 3 separate issues that overlap a little)

Politics

Conspiracy Theories

New Forumites (not here thank God)

Science Fiction (you know, the old "do cyborgs have rights?" argument)

Games (I pwned you nubz)

You forgot vegetarianism.

God!