I won’t presume to speak for others, but an example I can speak to from my personal experience:
A few years ago, a female character was confirmed gay. I didn’t know the story or the character, so this didn’t really affect me either way. However, men on sites like Reddit started throwing absolute tantrums. They said horrible things about lesbians, and a lot of it was difficult to read. Not using Reddit, I wouldn’t have seen any of this. However, many people thought these posts were funny in that they were pathetic, so they shared screenshots here. All night long, people I followed who weren’t lesbians reblogged the tantrums, laughing at these sad men, and the obvious point was to support the decision to make the character gay.
However, all I saw for about 12 hours were screenshots of the most heinous lesbophobia imaginable being reblogged by non-lesbians in what I believe was an attempt at support and solidarity.
I didn’t feel supported. All I felt was the reminder of how much people hate who I am, and the horrible things they will say to express that.
Had these posts been intermixed with positivity and affirmations of the goodness of being a lesbian, it would have been different.
I think we find it easier to share and balk at anger, outrage, and hatred, and we end up unintentionally exposing marginalized people to excess ugliness that of course they know exist but didn’t necessarily want to see from every angle all day.
Again, I won’t speak for marginalized groups I don’t belong to, but I personally would like to see more positivity surrounding Autism especially, especially every April, instead of 570 posts about the abuses Autistic people suffer, shared by Allistic people, with no positivity as support mixed in whatsoever.