I have a question though- what could be the appropriate sanctions for a person intentionally spreading libelous and unfounded claims against a project? Clearly, there has some sort of damage that OP incurred due to the spread of malicious words/statements that affected the general feedback of his project.
If he did spread false accusations on this forum, I have no doubts that he would end up with negative feedback. But since he did it on the external sites (and its not easy to be 100% sure he is behind it), neutral is just fine, and that's exactly what he received from a couple of members (Including me).
Don't conclude your judge on the experience you had with a member, you could have been in thw same shoe if you're a newbie or legendary rank doesn't mean youve got everything it takes with good reputation, and i say it again that you should report him provided that you have life evidence to proof your claim to ascertain it with reference pointing to the whole scenario, if not your tag on such member may be invalid without a reference.
Maybe I am wrong, but I think that OP meant crypto space in general and not this forum specifically. he is right though, this space is extremely toxic.