It's just a personal choice. I'm the type who's able to divorce my opinion of an artist from their work fairly well, but I can understand why others might be a bit more uncomfortable doing so. Frankly, some of my favorite artists (particularly some of the older ones) are people I'd gladly punch in the face. Orson Scott Card isn't even close to being counted among my favorite artists, but I might see the film at some point (especially if John Scalzi is right; if there's any chance that the likelihood of an Old Man's War film hinges on the success of Ender's Game, I'm there), and I'm very much someone who believes opposing gay marriage is, of nothing else, the pinnacle of self-indulgent moral policing. Since even Card admits by this point that he fought a losing battle, I'm not very concerned with whatever percentage of the films proceeds going to him. At this point, there's really very little he can do with it. It was one thing a few years ago, when he was using his profits he made from his books to actively campaign against gay marriage. Now he's just a cranky old man. I fund a cranky old man every time I buy a Star Wars book.