The fact that you don't quote a message doesn't change that you push the thread back to the top.
To stick with the example of the forums, I can dig up an old thread where there's some hefty stuff that is against the rules which has been missed for some reason, respond to one of the posts that are not against the rules, and there we go - nothing the mods could do against it (well, unless they bend the rules after they have figured out that that's why I'm digging up old posts). The thread would get closed because of a necro, there might or might not be infractions issued to the people who violated the rules in that thread (depending on how the mod in question handles content that has been inactive for ages), but neither of that would stop the fact that those posts have been made visible again, and nothing I have done was against the forum rules. Perfect troll job - maybe I'll do it some day.
That is for all intents and purposes me "republishing" the information as a byproduct of commenting on something in the same thread. (Which I'm aware isn't quite the same as liking something on facebook, don't forget this is still part of the "Where does it stop?"-question.)
Yes, there absolutely is a slippery slope. And there're a billion scenarios that I am not in favor of. But the Facebook 'like' feature does two things: it brings something to your friends' feed and it's
at least an implicit endorsement.
Even the Facebook 'share' feature allows you to add your own commentary, which means that it can republish something odious AND give you the opportunity to discuss it. To refute or chastise it. That one would create an even more slippery slope, since I could share libel and then use a strawman rebuttal that causes people to kneejerk response to dismiss future criticisms.
I really do liken it to CFC's policy of being responsible for what's in your own forum post. If you're reposting foul content, then you're responsible for it, in a clear and obvious way.
Bumping a pornographic photo on CFC with a 'This is great' would deserve an infraction.
Trump's retweeting of a racist and false infographic deserves chastisement and contempt.
And liking a libelous post on Facebook is libel itself, at that point, the mechanisms of the tort process kick in.
Remember, too, different jurisdictions have different thresholds for the libel tort. In the UK, iirc, the defendant has to prove that the nasty thing is true - that's a horrible burden that journalists hate. In the States, the plaintiff has to prove that the nasty thing is false. That's a heck of a burden for someone. In both cases, the deeper pockets have more power, by a large large margin. And in States that value free speech, you have to give up a LOOOOT of privacy to sue someone for libel.
But that doesn't change the nature of what liking a Facebook post does!
