Because non-supporters of the President will do anything to find something about Obama controversial.
Personally, I don't care if he thinks Kanye is a jackass or the nicest guy in the world. His opinion of Kanye is the least important of matters, and there are bigger issues to be concerned about.
It isn't like he is just calling Kanye a jackass out of the blue - most other people in the nation familiar with the situation think the same thing.
As he quoted, cut the President some slack!
"We like to snark around here. Sometimes we actually talk about theater...but we try not to let that get in our way." - dramamama611