Owning firearms is, of course, more expensive than karate.

There's pretty much no such thing as an 'accidental' discharge. There are only careless mistakes, often made by people who shouldn't have been allowed near a gun in the first place. Proper firearm safety should always be practiced.

Hammers are dangerous. People have been killed by hammers, both by accident and on purpose. Hammers can do an incredible amount of damage and as a result are excellent for self defense. Kids shouldn't play with hammers because they might get hurt. Why does nobody care who has how many hammers? Why does nobody think it's "sad" that people own hammers?

A gun is a useful but powerful tool just like a hammer. If you don't know how to handle one safely then don't.