At the risk of perpetuating this discussion; if your property is contraband, the government hardly needs any more reason than that to confiscate it. Warrant, no prob.
You and I are at a museum and I see a painting that is beautiful, you see a pile of vomit. The idea of police coming in and taking guns away is as shocking to me as police coming in and taking away Bibles, gold coins, stamp collections, collectible cars, furniture, etc.. I can't see why that would ever be ok.
An AK is not a 1909 SVDB penny, let's remember that. A somewhat better case can be made for AWB: our government is charged with ensuring domestic tranquility and public safety, which are shaky at times in the big city. Me, I think I ought to be able to play Lawn Darts, but they don't. What are you gonna do? Given that Hitler Jr. is not on the horizon, military-style assault rifle ownership is not something I'm willing to get myself and my loved ones shot in the face for - especially when I can still have a buttload of other pretty effective firepower if I so wish. Simple as that.
