Well of course it was a PR disaster, they "fixed" it by removing the original blocking functionality altogether!

Both "don't show me their stuff" and "don't show them my stuff" are useful, they just shouldn't be bundled.

I don't think "don't show them my stuff" is a legitimate option for a publication and broadcast platform like Twitter. It's so simple to evade the blocks that all it does is promote sockpuppetry, which just complicates attempts to control all that "harassment" (which, more often, is actually just simple disagreement) that Twitter users are concerned about.

If you don't want your tweets to be publicly visible, set your account to private. If you do want your tweets to be publicly visible, keep your account public. Those are the two valid options. "Blocking" someone from seeing your tweets just puts them an extra click away (the "logout" button). It's online security theater.

The point isn't to put some ironclad barrier between you, it's just to make it harder for them. That's enough to get a lot of people to just give up and move on. If people want to do it, why not let them? Social stuff doesn't have to be all or nothing and it doesn't have to be perfect. The lock on my front door won't keep out a determined intruder, but it's still extremely useful.

A locked front door provides basic protection for a private domicile. Twitter is not private. A more apropos analogy to Twitter's block functionality would be holding a meeting in the park and yelling at certain people to stop listening because you don't like them being around. You can yell all you want but you can't actually stop them from hearing you or listening if they're interested, and it's unreasonable to expect to be able to do so.

Regardless, the fact remains that some users find this functionality useful. You can tell them it's useless as much as you want, but they want it, and Twitter provides it, so there's no particular reason to take it away.