There are a lot of good reasons to recast a role or write a character out of a movie. That said, I'm not a fan of this petition to have Amber Heard replaced in Aquaman 2.
It doesn't matter much to me personally. I didn't see the first movie and I have no desire to see the second. If the role is recast because the studio figures that the petition is a sign that too many people will refuse to pay to see the movie, I guess that's valid. Somehow, I doubt that there will be a significant amount of people who want to see the movie who will stay home because of Amber Heard.
I've never been a fan of Amber Heard as an actor; but, James Wan decided she was the best person for the part for whatever reason. People in Hollywood have done far worse things that Heard and kept working.
Basically, I don't like the public pressure in terms of making the decision. The decision should be made by the director and the studio without having to deal with these activists.
If they move on from Heard for the same reason that The Dark Knight moved on from Katie Holmes, which was to get a better actor in the role, that's valid. If too many people involved in the production are good friends with Johnny Depp and would be uncomfortable working with Heard, that would also be understandable. Making movies is hard enough without distractions. If she's going to be a distraction, it's fine to move on from her.
Still, some of these decisions to recast roles have been ridiculous. Reshooting Kevin Spacey's scenes in All the Money in the World struck me as a bad choice. I mean, I've always loved Christopher Plummer and recasting the role didn't destroy the movie; but, I still want to see the version with Spacey and I know I wouldn't have skipped the movie if he were in it.
It's not like people a ton of people stopped going to Roman Polanski movies. I'm not going to stop enjoying his art and there's nothing inconsistent with me thinking he should go to jail while also loving his movies.