I didn't hear what Sherman had to say. From what I've seen of the reactions to his rant on Twitter and elsewhere, I don't want to see it.
It started after the last real play of the game, where Sherman made the play to secure the win. He ran up to Michael Crabtree, spun him around and did a choking guesture in Crabtree's face. That earned him a taunting penalty, but it didn't matter. After the game Erin Andrews asked him to describe the last play. Instead, he yelled into the microphone:
"I'm the best corner in the game. When you try me with a sorry receiver like Crabtree, that's the result you're gonna get! Don't you ever talk about me! Don't you open your mouth about the best or I'm gonna shut it for you real quick!"
It wasn't obscene or anything, it was just about as poor as sportsmanship as you'll ever see at any level.
And this is not an isolated incident. He has a habit of confronting and taunting opposing players after the game during the post-game handshakes. Some people like that, I guess.