I don’t think anyone involved with HP has ever once backed her up with full-throated agreement that her views are correct. The closest they’ve ever come is “she’s entitled to her opinion, nothing she’s said warrants this level of vitriol”. A few of them put an “I don’t agree with her, but…” disclaimer on their statements, but for the most part still clearly stated they liked and respected her.
The list of people decent enough to publicly show a shred of loyalty includes Ralph Fiennes, Robbie Coltrane, Helena Bonham Carter, John Cleese, Jim Broadbent, Miriam Margoyles, and Evanna Lynch.
Jason Issacs and Tom Felton just refused to condemn her more than anything else. When pressed in interviews they refused to directly address anything related to trans politics (can’t blame them) so they get accused of fence-sitting.
Eddie Redmayne (he’s in the Fantastic Beasts movies) is an interesting case. He gets away with it because he made a big deal about how much he loves troons, but also felt bad enough for the abuse JK Rowling was getting that he admitted sending her a private letter of support.