You know, it's been my personal opinion that some independent works should be judged independent of authorship.
Yes Card has some failings as a human being. Heck, most human beings have failings. I don't see people lining up to stop buying Apple's because Steve Jobs was a shit father to his illegitimate kid. I don't see people burning Wu-Tang cds because ODB was into running guns and quite probably killed a few people. The reality is art can stand on its own.
A novella such as Ender's Game does stand on its own.
I'm a fan of another Sci-Fi piece called the Giant's Trilogy ( Gentle Giants ). It's a fun read. However, the author apparently was discovered to have neo-nazi leanings or something, and his popularity vanished. The book still stands on it's own as a solid work worth reading.
Going godwin, or really von braun... the man built v2 rockets for the nazis. But we still laud him as a hero of the US space race, because he helped design the Saturn V and put man on the Moon. One work bad, another good. But Von Braun not a wholly good person by anyone's definition.
At the end of the day, I say allow even the worst of us to contribute in some positive way to the world. Denying someone the right to contribute to society, because of some failure in their personality will make the world a sadder more awful place. And that's just the way of it.