On: You probably don’t need ReCAPTCHA

[inferiorhuman]

So how does one block this?

[sli → inferiorhuman]

Firefox and uMatrix[0], and then never go to those sites again, because you won't be able to use them anyway. Whether or not you want to contact the owner of the site and tell them what's up is up to you.

[0]: https://addons.mozilla.org/en-US/firefox/addon/umatrix/