I immediately thought of the Whole Foods debacle, where the founder or CEO (I’m unclear on this point) wrote in an editorial that health care was not a right. Whole Foods has a very liberal customer base, so of course they were up in arms over this ‘betrayal’.
I think it depends on the product and personal choice. If someone voted yes on Prop. 8 and I was a gay-rights advocate, I might not buy the clothes this person designs because I want to send a message about what I support. But I think it’s unfair to force public figures to have no opinions just because they could offend their customer or fanbase.
If I believe I am supporting a cause I find hateful (not just distasteful, which I can live with) significantly through my purchases, I will boycott it. Sometimes because I hate the thought of my money being used for something against my principles, and sometimes just to make a statement.
But I think I’d let a lot of small issues slide, or ones that I think are irrelevant. I won’t stop listening to music because I disapprove of what the singers or band members are doing in their personal lives. I just like the music. I listen to it on Youtube mostly, so it’s not like I’m paying them. If they’re using their fame (from that product) to do something I’m against, that might be different.