I'm unsure how this became a fad here however here's my thoughts on these guys. First of all I have a few characters that are a little bloodthirsty and some that enjoy the suffering of others(Yay schadenfreude!) but not like 'devour your own species' kinda deal. These groups were probably started by minors trying to jump on a bandwagon, and boy haven't we all jumped on one.
I never crossed paths with any of these groups or even a character who happens to be cannibalistic besides a few Creepypastas, and I do not wish to join such groups. I appreciate if they keep their visceral roleplay in private chat at all times because compared to how violent my roleplay can get, theirs may cross the line however. So when in doubt, roleplay in private, or use a different platform to roleplay with another person.