Some of his material may seem crass, but he's a satirist. And he's catching our attention in a way so blunt and in-your-face (which--by the way--is what seems to appeal to the American public--crass humor).
He gets his point across--most of the time. It's disturbing how many people -don't- realize that his films are satires... I'm sure that many people thought that Jonathan Swift was pushing it too far, too, back in the eighteenth century.
I do feel a bit uneasy comparing Swift to Cohen, though...