Because he doesn't. Every supposed quote I've seen which could support your claim is either partial, or flat out ripped completely out of context. So no, he doesn't agree with democrats about "assault weapons." A term, by the way, which is a verb and a noun put together and invented by politicians to evoke a sense of fear from those who don't understand that there really isn't such a thing as an "assault weapon" in real life. There are only weapons used in assaults, not assault weapons. Furthermore, anything could be used by someone as a weapon, with varying degrees of success depending on what the object is, though used as a weapon nonetheless.