See, this is why I sort of think it's funny. It's a "secondary reaction" joke. The joke itself is lame. The humor comes from imagining the reaction of the thin-skinned Obama and his hyperprotective partisans in the press. Then, of course, seeing it.
I think this is a type of clapper humor we see a lot from liberals, especially Bill Maher. His "jokes" aren't funny; but people laugh because they are anticipating an angry, upset reaction from the right.
So, it's not a style of joke of high craftsmanship. But it is one that has long had a cherished place in the leftist toolbox.