2. Can you tolerate an author's presence at a convention if their politics/values offend you?
Repeat variations ad infinitum.
Orson Scott Card's the obvious one here. But I have authors I'm not inclined to read because I've heard of or witnessed offensive behavior on their part. And there's one author in particular whose blog I wish I'd never discovered; I was (am?) a big fan of his fiction, but his blog veered into raving right-wing loony territory. I have books he's released since then, but they're lurking down by the bottom of the to-read pile, because I do not know if I can enjoy them now.
EDIT: And this is not meant as a right-wing/left-wing thing so much as it's about how the authors in question treat other people.
ALSO EDIT: And OMG Dave Sim. How did we forget to talk about him in the Misogyny in Comics panel at Arisia?