We know they did vet the tombstones.
What I don't get is, specifically, what the problem with this tombstone is. Are we saying that in-game characters can't be transphobic? Homophobic? Racist? In other words (even though this is backer content) why does an in-game character being clearly transphobic* (to the point of killing themselves - not the trans in question) translate to Obsidian as a company, individual employees - or even the backer who made that content - being transphobes (or anti-trans) themselves?
Because this kind of corollary logic (it exists in the game, therefore the makers of the game support this) is pretty unsupportable, IMO.
Spoiler for POE:
*I suppose this is transvestite phobic since the guy was able to find out she was a man. I haven't played PoE long enough to know whether the setting supports transexuality or not to be honest, but if magic can make someone a woman, I'm not sure how you'd find out she had ever been anything other than a woman.
**Obviously I don't think this is true, but this is why I think this kind of argument is a slippery slope.