The poll doesn't mention zombie attacks. I guess that makes sense, I'd probably get more use out of a shotgun (or a chainsaw or a machete) if/when the zombies come, depending on the situation at hand. Are the zombies coming? The Chinese? The Russians? Crazy people high on bath salts?
I don't know for sure. Neither does anyone else. That is why I prepare (thank you, Boy Scouts). When I go camping, I take a rain poncho with me even though the forecast calls for sunny skies. I have several tools in my garage that I rarely use, heck I have a tool that will cut right through a cast-iron sewer pipe that I don't ever plan on using...But if I need to use it, I have it, and I know how to use it.
My point is that a situation may arise when the ownership (and knowlege of proper use) of a semi-automatic rifle would come in very, very handy. If the zombies come, do you want to stick with that frying pan, or would you rather have something that packs a little more oomph? Exactly. If the zombies come, I either want an assault rifle or I want to be very, very good friends with someone who does.
On second thought, I'll keep my semi-auto. Here, you can use my machete (or even my sewer line cutter). Best of luck.