In my experience some of the most toxic criticism short of physical violence comes from not acknowledging what someone believes are logical conclusions.
So wearing a dress is fine if the person wearing it is willing to concede at every moment that they're being socially deviant. The moment that you just wear a dress and make no attempt to justify yourself in terms of larger culture is when things get bad. Wearing a dress and acting like it's no big deal is an affront to the logic of someone who knows for a fact what you're doing is deviant..and they're convinced that you deep down know it too. You're more or less saying they think wrong in a very fundamental way. That gets people very upset.
Dunno, if I saw a guy wearing a dress I won't see it as "deviant" at all. I might glance for a second, acknowledge, and continue about my business. I don't care what people wear. That said, many people _do_ care, which I don't really understand. Unless it has racist/sexist/prejudiced text on it, wear whatever you want.
It's deviant in the literal sense - that is, it's not normal. I don't the he was trying to pass moral judgement or suggest that the dress wearer is some sort of pervert.
If you saw a guy in otherwise ordinary circumstances wearing a dress and didn't think it was unusual, well, you lack situational awareness.
So wearing a dress is fine if the person wearing it is willing to concede at every moment that they're being socially deviant. The moment that you just wear a dress and make no attempt to justify yourself in terms of larger culture is when things get bad. Wearing a dress and acting like it's no big deal is an affront to the logic of someone who knows for a fact what you're doing is deviant..and they're convinced that you deep down know it too. You're more or less saying they think wrong in a very fundamental way. That gets people very upset.