> Some silly people think this isn't possible, but if large providers are forced to do it, then they can easily tell smaller ones they'll be blocked if they don't also do this, and so on, and we'd have a slightly more responsible Internet again.

You go ahead and force a large provider to do it, and let us know how. From what I can tell from reading NANOG mailing list posts off and on for decades is that most of the larger providers really won't be bothered to do this, and there's not any effective leverage to force them.