These photos have a goal: to make conservatives look foolish. The attempt will fail; Americans don't think any less of their President because he has a bladder...and they are able to understand if one focuses tightly on one particular body part a caricature of the person will result.
The press is at a point, now, however, where they will try anything to see if Bush can be taken down. :) They're like kindergarten children fighting on a playground, only not as mature.