Why does sexism exist?
Because the other sex is inferior. 
Your OPINION is a bore…I hope you got more than that to come back at me with;) or perhaps you prefer to stick with it and fade out like the rest of the ignorants.
Reported for forum change.
Moderator action
Maddog Mystique, welcome to the Straight Dope Message Board. The General Questions forum is for questions that have factual answers. If you wish to debate the topic, the Great Debates forum would be most appropriate for that. If you wish to get the opinions of other users, the In My Humble Opinion (IMHO) forum would be better for that. IMHO is not a place for debates, though.
While this question can be answered factually, that doesn’t seem to be the intent of the OP. Because of that, I am going to close this thread. Those who wish to discuss other variations on this topic are free to open a new thread in the appropriate forum.