I've wondered what it was about the different way Clinton and Obama are attacked in the media and online. I think I now understand.
Explicit racism is just no longer accepted in this country. At least not out side the klan and klan lite folks. Therefore, when Obama is attacked it is necessary to use code words and phrases. Oh, you can still attack him racially, but it has to be done in an acceptable way that doesn't use the (gasp) "n" word.
Sexism is I think alive and well (racism is too, but it has to be covered up a little -- not too much cause we do want the knuckle dragging mouth breathers to get it). Sexism can be engaged in without the apparent need to use code words. You can call a 50 year old woman a girl, but you really can't call a 50 year old African American mad a boy. If you do you are forced to kind of sort of apologize for it. The same I think for the harsher "c" word (although really used in comments and locker room discussions) and "n" word. You get away with cunt much more ofter than you will be allowed to get away with nigger.
Of course, all that doesn't mean that there isn't enough hate to go around.