Looking back at the boycotts of Ender’s Game and Twilight during Prop 8, I think the current attitude of “if you participate in even the non-commercial aspects of Harry Potter fandom, you are just as bad as the people giving money to Rowling” is part of the rise in purity culture in fandom over the last decade.
Orson Scott Card gave money directly to the 2008 campaign to ban same-legal-sex marriage in California, despite not being a resident and thus acting against his own self-proclaimed respect for state’s rights, because his homophobia was stronger than his principles.
I don’t remember if Stephenie Meyer gave money directly, but the Mormon church was openly donating and campaigning for it, and she was known at the time to tithe.
So we all said, don’t buy their books, don’t buy tickets to the movies, don’t buy the merch, don’t give those authors money.
While there might have been some pockets of “don’t engage with their works at all!” generally fandom was still considered fine to keep trucking along in. Sure, draw art. Write fic. Make rec lists, character playlists, cosplay. Have your fun, just don’t give the authors any money, be it through direct book sales or through associated royalties.
Now, though? With J.K.Rowling openly giving money to groups harming trans people, openly speaking out against trans rights, we’re once again calling for boycotts...
And the fandom is tearing itself apart, with people insisting any engagement whatsoever hurts trans people. That talking neutrally or positively about the series online, or posting fic, or art, or cosplay, or other fan crafts, is the same as personally acting as a marketing department for Rowling, and therefore is going to get other people to buy works or merch from the franchise.
Or that having HP related graphics or text on your blog, or wearing old merch or cosplay or self-made accessories where other people can see you, is openly signaling to trans people that you don’t care about them. Or even that you are actively against their rights.
This...was not a thing during Prop 8. Fandom was not saying “your Livejournal icon with an Ender’s Game quote is going to funnel money to a hate campaign.” We were not saying “cosplaying Twilight characters signals to all the queer fans that you believe they shouldn’t have the right to marry.”
For good or for ill, fandom has drastically changed.