I am not an American, so it is hard for me to judge, but I think a big reason for the racism is the lack of other things the Republicans could use against Obama.
Virtually all problems you guys have at the moment (economic crisis, wars, etc.) are the direct or indirect results of 8 year Republican (mis-)management.
It is hard for somebody who run a huge deficit during a boom to blame Obama for handling the crisis poorly.
My two Euro Cents
Edit: Ups...I missed the topic.
Anyway, I think it is important to avoid discussion about such attacks, because otherwise the Administration gets bogged down in a huge racist controversy.
So count me as one of the people who doesn't speak up against racism in this case.
Edited by Simonster, : Missed the topic