since zig is famously decentralized, i don't think there is a way to effectively combat bad actors like these? there is no "official zig org" that can disown them

Its the opposite in my understanding. Zig has a BDFL.

Trademarks are the usual cudgel of choice to enforce a bad actor claiming to be part of offcial Zig.

In a decentralized but communicating community, this kind of post is raising awareness, and then the others in the community will make their own choices regarding the matter.