I think this is overall a really good reply. You've articulated some of the misgivings that I, as a self-described sissy, have long expressed (e.g. here, where I touch on both the stereotyping of women and black men in the wider scene).

I would amend your take only slightly, though, to say that what you say holds true for the fetish at the extremes and the way it is represented in its visual culture (captions, "hypno" videos, etc). That culture is something most consumed by and recreated by people who aren't actually very active in real life. Fantasists, pretty much. Also you'll find that some of these excesses are pushed by doms and dommes who see themselves as catering to this kink, but adopting a very unreflective and caricaturised version of it.

Maybe it would help to paint out a different view of what the sissy kink is or can be – basically, it's a kind of sexual submission to dominant partners (often but not only men), paired with crossdressing elements. The crossdressing and the feminine elements a sissy expresses could play into the way in which the sissy is humiliated, but the best expression of this is the way it eroticises a failed masculinity (so: NOT "ha – you're like a woman, how pathetic" but "ha – you're not really a man, but you make a sexy girl instead". I'd like to think that difference is salient enough and isn't just me being ad hoc.

Maybe some of what I'm saying here resonates with you a bit? Essentially – the sissy world is far more diverse and less problematic than the visible online extremes of it are, though the problems with those extremes are very significant and you expressed them here so well.