Any sensible person would say that what this guy was wearing was inappropriate, but when you're so far down this rabbit hole, people just can't.
It's not nice that people become involuntarily involved with this guy's fantasies, but I don't know how legally classify that, unless he had clear signs of sexual arousal (which then becomes a child protection issue). Perhaps even us mocking the guy is helping his fantasy? (Not a pleasant thought).
After seeing a lot of young teenage boys (through links on GC sites etc) being told that their sexual fetish is in fact gender dysmorphia by various pressure groups and charities, I grew worried about a whole generation not even knowing that it is that.