It’s a little bit of both of what you listed. Enjoying Harry Potter on its own is generally fine… The problem I have with it personally, especially in this case, is that JKR has specifically stated multiple times that the funds from it go directly to anti-trans organizations.
People are allowed to enjoy whatever they want to enjoy, but if that thing directly funds hate… I am likely to think less fondly of them.
Similarly, if someone says their favorite person is Andrew Tate, I probably won’t match with them.