Disgusting, but it's only natural. The little guys don't have the resources to fight it out in court and keep their heads above water, so trolls can extort a small settlement or licensing fee from them. Ironically analogous to trolls in fairy tales that would extort characters under dubious pretense.

Trolls are weak against fire and acid. Just sayin'.

Indeed, hypothetically, if a tiny game developer had gotten such a letter, they would probably be asking their friendly lawyer to find a moment to advise them, rather than saying anything publicly. I suspect a great many such extortion letters have been sent; let's hope they sent so many that the combined defense will be enough.