Ozzy is awesome. "No More Tears" is my all time favorite song. Personally I wouldn't be suprised if Ozzy didn't know about the Bush bashing stuff. I saw one of his TV shows where he was invited to a Bush Correspondents dinner. He seemed extremely happy to be there and was given an ovation when Bush joked that his mom loved Ozzy's stuff.
Anyone who's watched the TV show can see that Ozzy is controlled by his handlers. I could easily see his handlers or concert orchestrators putting the Bush bashing in without his knowledge.
Ozzy is controlled by Sharon, and by the residue of countless toxins and hallucinogens he's consumed through the decades.