So just because Michael Kay says it, it's true?
Was Carlson standing where he was standing to antagonize the Yankees? It's possible. However, it's also possible that Carlson gave a half hearted attempt to back up home plate because he was upset about giving up the hit and realized that the odds of their being a play at home were extremely unlikely.
It's unfair to talk about what Carlson did as a fact, when it's nothing more than conjecture.
Here's what we do know. After two Blue Jays got hit by pitches, they were perfectly in the right to throw at a Yankee. There was nothing wrong with how Carlson did it. At the time Posada's emotions got the best of him, and that's fine. I would have preferred if he had just brushed it off as part of the game, but so be it. However, over the next ten minutes (between the time he was thrown at and the time he scored) he needs to be able to get his emotions in check. He was completely out of line to elbow Carlson, and he directly caused the entire brawl. Posada is completely in the wrong in this situation no matter how you slice it, and it's debatable whether or not Carlson was in the wrong.