I think what's mainly wrong with the poster is not Paul Blart himself, but that background. It should have always been a mall background, or a much faker looking sky to appear like it was taken in a cheap photography studio.
You guys are taking it way too seriously. It's a parody. The guy is a mall security guard, and they take themselves way too seriously. Hence the serious look, the cloud background. The poster is how he sees himself. Now, as far as Hitler, I don't really see it.