I can't believe in this day and age we allow people to have knives.
Knives have other practical uses besides killing...
Oh, like a say... a gun.

Guns are for killing. Nothing else. Unlike cars, trains, planes, knives, axes and lawnmowers.
So the law should be that you may own things that have practical uses?
I would, in general, prefer a limit on devices whose sole purpose is killing. Art, flowers and pastries don't necessarily have practical uses, but I don't see any serious problems with them.
Just playing devils advocate here.
Then play it well, if you're going to do it at all.