Just saw a thread on the underground (a place that is tough to take at times, but when things like the thread in question happen its a fun time) where some fellow who was lying about being a black belt got exposed, and brutally.
In this guy's case, I am sure he is way over-resenting his level of knowledge or skills.
In general though, a few good rules to keep in mind when curious about a fellow being "legit", if he claims some level of ranks of note (I would say purple belt or shirt, or higher) I would look for the one thing every BB I know has, a picture of them being awarded this rank, or direct contact info of the guy who awarded this rank.
Another thing I would look for, is if the instructor at a place isnt grappling the students consistently, its a red flag.
And lastly, a lie is a lie. What I mean by this, is if a fellow is of a lesser rank, says he is that rank, and offers to teach with all his qualifications on the table, two thumbs up. "Official" rank is certainly not an end all be all, and there are plenty of legit guys who lack it, but they N E V E R lie and say they are more ranked than they really are, IME. Any lie about qualifications is, in my experience a preview of things to come with regard to finding alot of stories later.
All that said, I ask to the OP, entertain us a bit with more stories about this guy, I am in the mood for em after the Torches and villages scene from the UG.