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Not really. Anything which can kill could in theory be labeled as something which can deter by threatening to kill. In which case, items whose primary purpose is not to kill, but can kill, have three possible uses, which is one more than guns. Those three functions being their primary purpose, killing and threatening. I really don't think guns have a primary function which is not one of the two: killing, and threatening.

Clearly the car analogy is an absolute failure, and only makes gun advocates look like stupid individuals who have no better argument up their sleeve. Furthermore, it makes them look like they can't think, as it's just a repeated mantra. It is a sad reflection upon themselves. And specifically, the car is so integral to people's everyday lives, commerce and the economy, that it just compounds the apparent stupidity of gun advocates. Best thing they could ever do to try and win some points with gun control advocates would be to drop that meme like it never existed. But go ahead and keep using it, and trying to make it seem relevant, if you wish to maintain such appearances.