That's what it's about.
Few fake expertise in a field just for kicks or for bragging rights. Frauds fake expertise in a field in order to capitalize on others' ignorance, just like that "black belt" in that Texas UFC Gym. He didn't fake being a black belt just to be the king shit at that gym, but instead he did so because he knew he could get a job coaching.
I'm aware that fraudulently taking money from people is bad. I agree. I don't have an argument to offer about that, but that's a universal idea not specific to being a BJJ black belt. I don't like child molesters either. The fact that they might also be falsely claiming to be a black belt in BJJ is irrelevant.
I know, I know, I can hear the "But they use that distinction to lure people in!" argument already, which is true. But that, also, is not specific to being a BJJ black belt. A person could claim to be an expert in any field to lure people in and we would still hate them for it. If you would only hate them if they claimed to be a BJJ black belt, but not if they claimed to be an expert gymnast, then maybe we would be on the same page. Somehow I doubt that would be the case, however.
I'm just making a distinction between the two. I don't care whether or not someone claims they are an expert at anything. Claim away. You can either back it up or you can't. I DO care whether or not they do terrible and/or deceptive things. One is a presenting problem, one is a fundamental problem.
If the issue is just about being a black belt, then I would also have to take issue with a person who was using their fake belt to do positive things as well, and I wouldn't. The fundamental "problem" (what they were using their false claim to accomplish) in the scenario changed, while the presenting problem (their false claim) did not. That's why no one cares about the guy who claims he can bench 400lbs, because the claim isn't the problem.
Some people, however, take issue with people claiming to be a BJJ black belt because they somehow think it diminishes the hard work they put in to earn their own belt. I don't feel that. I also don't feel like the guy who claims to bench 400lbs is diminishing my ability to bench a lower weight.
Am I overthinking it? Probably. But human behavior is what I do for work and something that enjoy exploring, so sue me