Ok, so, I have a few problems with this take.
I do not think it healthy to consume content made by hateful people.
First, I question the very premise. That consuming otherwise benign content is somehow "not [...] healthy" if the creater is themselves hateful, whether or not that hate is present in their content. A) by what do you mean it is unhealthy? For your mind? Your eternal soul? What? B) If the content does not display any of the specific hatred of their creator, by what means would that hatred effect me at all? Psychically?
Second, let's assume the premise is true. Tell me then, how would you ever avoid this unhealthy situation in your life? Sure you could avoid the openly hateful creators, but how would you ever know who is secretly hateful? Many a creator of beloved works, has turned out to be an asshole or a bigot. And many of those were only revealed as such after those works became beloved. Surely, many more were also created by hateful people who were not and may never be publically revealed as such. Given you have concluded that the content and monetary support is not all that matters, but also the internal character of the creator, how do you know your health isn't be constantly compromised by consuming work by people you don't know are actually hateful in some way.
Third, it seems kind of a moot point anyway in this case. Rowling only started revealing her transphobia in 2019. By that point the entire novel series, the entire film adaptation series, a spin off play and companion book, the first two of three spinoff films, and any number of video games, toys, and other merchandise had all been released and consumed by billions. The vast majority of our generation has consumed a ton Harry Potter media in many forms before her bigotry was on full display. I personally read most of the books over and over as a kid. I gotta tell you, if my health was damaged because she was secretly a hateful bitch at heart, then that damage is done.
I get wanting to take a moral highground, being disgusted by the association, and just wanting to distance yourself from Rowling and leave it behind. I truly get that and think it is entirely justified and valid. But don't project some sort of damage onto people who don't do the same, or attribute some sort of complicit immorality to them because they don't take the same stance as you. That's where I strongly disagree.