Ive always wondered what sort of gross fetish thing she must be asking for that makes Meatball go "Whoa now, hey, lets just slow it down a bit babe, I'm not doing that, jesus fuck, thats messed up."
Maybe it isn't gross at all. Maybe he's cool with the gross stuff. "I'll let you take a big, steaming dump on my chest, but I will not be having missionary position sex with you."