You don't have to know anyone to read that comment as satire. I suppose Facebook would also have banned Johnathan Swift for his "Modest Proposal". https://en.m.wikipedia.org/wiki/A_Modest_Proposal
Surely you see there's a difference between a Modest Proposal and posting a Facebook comment suggesting someone should die with no other context informing people it's a joke?
Doesn't the context of billionaire endangered animal hunter inform us that it may possible be not-serious.
Surely?
On the other hand, there's bound to be people who believe fair-trial-judicially-decided capital punishment would be fair retribution for anyone who intentionally kills endangered animals.
I'm going to say something like: I'm against capital punishment because it tends to kill innocent people at least occasionally, not because it isn't often deserved.
The point of a comparison is that there is a parallel, not a difference. There is always a difference.
What is the parallel? In both cases, people who did not recognize the author's point took offense. (And yes, a lot of people were seriously horrified by Swift.) And in both cases the author's actual point was close to the direct opposite of the one that those people thought. Some people found obvious, others didn't. To people who found it obvious, it can be surprising that it wasn't obvious to others. People who didn't find it obvious think it a horrible thing to say.
In this case the comment is directed against the justification that the billionaire offered that it is OK for him to kill the animal because he paid lots of money to do so. And her point is that just because you pay lots of money to do a wrong thing, doesn't make it OK to do that wrong thing. To see it, put the billionaire in the animal's shoes. How much money would it take to make hunting OK? Obviously no amount of money would suffice! Just as the billionaire's having paid lots of money didn't make his hunting OK either.
That said, this one actually gets complicated. The money from these hunts goes to anti-poaching efforts. So the billionaire kills one animal, and his money saves others. Which still makes the billionaire a shitty person, but there is a utilitarian argument for allowing it.
That said, how would you feel if we were talking about hunting children dying in a famine instead of black rhinos on a preserve? The same utilitarian argument applies, but I think most would be for putting the billionaire in jail. How you feel about that is likely close to how that friend feels about what actually happened.
Ultimately I'd prefer nobody was threatening kill anyone in any context on a social media site, no matter how witty they think they're being. It doesn't seem like it should be such a high bar to set but apparently it is.
The whole point of an anonymous complaint system is to allow accusers who might be intimidated by the idea of confronting you to have a way to get their concerns met.
Which means that anyone who has created an anonymous complaint system has traded off your right to confront an accuser with the accuser's right to not be intimidated and decided in favor of the accuser.
However there is usually another counterbalance, such as having the accusation silently disappear unless a neutral third party thinks that there is a point to the accusation.
Did she know that the person she directed that comment to did not know her?