IE, show them this: http://i.imgur.com/XZmPlGQ.jpg, and the response will be "Yeah! Ban that! Nobody should be able to own that!"
Show them this: http://i.imgur.com/a916R.jpg, however, and the response will be much more muted, perhaps with a bit of "I think my Dad had one like that for hunting or something..."
Of course they are functionally equivalent rifles, each semi-automatic. But one looks scary/bad-ass, one looks like Dad's hunting rifle.
I don't mean this all argumentatively or semantically. I think this issue really matters. If we are going to pass laws based on the outward appearance of something, then that's the kind of law - and legal process - I am very wary of. If, instead, we have an honest and reasoned debate on the issue, going through a process of deciding if, say, semi-automatic weapons should able to be owned by citizens; and if there should be a limit of the number of rounds in a magazine - or if people should be able to own a rifle that accepts a magazine; then that's the kind of process I can get on board with.
I think it's dishonest to ask a voter, "should we ban assault rifles?" I think it's much more honest to ask, in effect, a series of questions about firearms, to get at the meat of the matter in a way that is sensible.
But I don't think I'm going out on a limb here when I say that as it stands, people want to ban scary looking guns, and that is the depth to which they evaluate the entire issue.