Evidently some of the story is that Wilson is also pissed about the Giants still using his image even though he plays for the hated Dodgers now. Baer, the G's President, denies that story, which came from a fan that sat near Baer. But it blends in with the idea that Wilson is really pissed at the team.
PL is correct, a lot of this ire comes from the Giants not picking up his option for 2013, and then not signing him during this summer. Which doesn't make a lot of sense, because no team would have picked up that option. Wilson was on his second Tommy John surgery, and the stats for people returning to good form after a second TJ surgeries is very low. And secondly, the Giants already had a closer in place in Sergio Romo. Wilson is the type to hold a grudge, so that's where this is coming from.
Funny, I was watching the game last night on the Dodgers feed, and right at the end of the broadcast they were showing Wilson going at Baer, and I'm screaming at the TV, "Vin, don't let them go to commercial" yet they did and we missed the story. Dang