I think we agree, although I don't find your point about authors needing more scrutiny convincing. I think any public person creates an example for their society, and that can be just as damaging.

However, my feelings regarding Card are more nuanced than just "respect/disrespect". For example, he has a blog where he gives information to aspiring writers. If I was an author should I ignore that useful information because I don't respect his moral views?

My current feeling is that information on it's own doesn't have a moral stance, and so I can respect his advice in one area but not in others. Yes, I agree this is a slippery slope, but I don't know what the solution is. Should I reject Fischer's advice on chess? Card's on writing? PG's on startups (because I don't agree that Lisp is a silver bullet? :))

particularly when they start using their talent to spread their hate, and start letting it seep into their other 'manstream' [sic] work.

I don't think Ender's Game showed any particular homophobia. There is some moral ambiguity in the book (which is kind of the point), but I didn't see anything very hateful in it.