This is ultimately one of those things where computer scientists (specifically) freak out because the real world isn't zeroes and ones like they're used to, it's all shades of grey, but if you act in good taste it's probably not going to be a problem. Ban the cartel murderporn, show the aftermath of the bombing (or not, at your discretion), ban the nudists, but allow breastfeeding (or not, at your discretion), all of that sounds fine to me and we don't need to code an exact line into law.
This is really a common thread in HN threads discussing anything touching on laws or regulation, because computer touchers just can't wrap their head around the idea that the law isn't absolutely precisely defined in a state machine and the judge and jury are going to apply human reasoning. But that's how the legal system works.
I'm going to note that there is of course a degree of self-servingness in insisting that there be an exact line drawn. It's a way for Facebook to punt on actually having to moderate their platform and push that responsibility onto the courts, because they don't want to pay humans to deal with what is ultimately a human problem that needs to be solved in human ways. The nature of the world is that there are grey areas and some stuff in the grey area is fine and some stuff shouldn't be there, and it will take human intervention to decide which is which.
If you don't want to pay to do that, and you want to be 100% on the green side of the line, then you will have to default to very aggressive censorship that will probably annoy users, but that's the price of being on a free platform that doesn't want to pay for adequate moderation.