Calling such posts grotesque and unpopular is quite euphemistic. They are aggressive and dehumanizing. And the determination on what should or shouldn't be protected as free speech doesn't happen in a vacuum: these attacks were targetted at a minority which is already regularly assaulted violently just for going about their day, because of violence-inciting shitposts like that. Of course you can't usually prove that post A led to violent crime B, but simply pretending like telling people over and over again that some group is criminal scum isn't going to lead to more violence against them also can't be the solution.
I also think that such laws almost have to be kind of vague by necessity, because the agitators will just try and be clever for plausible deniability. The idea is that a judge will rule on it, and the accused gets legal representation to defend their case. Of course you can always find some case where you may think the ruling was too harsh (or too lenient), but overall, the system seems to work pretty well. You really have to dig deep to find one or two iffy cases.