(WARNING: Semi-Long) Why would this guy like me when he knows we're SO different?

Hon, as long as you're willing to actually have a discussion about the kind of guys you like with him, he's going to see that as flirtatious negotiation. Media and literature are full of bickering couples whose arguments culminate in a kiss; maybe he's expecting this to go the same way. If you really want him to leave you alone, tell him once that you don't see the point in continuing to discuss it since it's not going to happen, and refuse to talk about the subject again. He can't try and persuade you if you're not willing to listen to persuasion at all.