So, it turns out that Dave Grohl's support for John Kerry at the last US elections wasn't entirely wholehearted:
During the last election I supported John Kerry on the campaign trail not as the guy from the Foo Fighters but as a citizen concerned about the future of this country. I did it because the Bush campaign was using some of our music at their rallies, and I didn't feel like the songs they were using made sense in the context of the message he was delivering. I couldn't stop them from using them; there's legally nothing really you can do. So I thought, Well, I'll go out and sing those songs at Kerry rallies, where they seem to make more sense -- songs about love and hope and compassion.
Oddly, he doesn't then go on to explain about his motivation behind playing gis in support of campaigners who claimed that HIV and AIDs were unrelated. Perhaps he'd heard some people with actual medical knowledge playing his songs and wanted to counterweigh against that.