Yes, that's exactly what I said. The feature is designed to address the "somewhat bad friend" case, not the "terrible friend" case. Both of those kinds of people exist in the world.

Reducing the chance of something that you didn't want shared from being shared by a factor of X% is better than nothing. Try to step out of black-and-white thinking for a minute. Just because something is not perfect doesn't mean it's useless.

I'm personally disgusted by tools which actively attempt to prevent someone from doing something which I myself can bypass just because I have the knowledge to do it.

Yes, your example of trying to prevent someone moderately bad from sharing something personal to you which you don't want shared is reasonable. The trouble is, you can use the same mechanism for much less reasonable and more nefarious, corporate things.

So the end result is that we're not to have moderately nice things, lest they be used as a weapon against user freedom by a mega-corporation.

I wonder how many people it actually stops from saving or sharing. If they want to save, they will. If they want to share, they will. I know you are talking about some people who want to save or share but is too lazy to take a screenshot or take a photo with whatever they can.