ESPN is not a Red Sox mouthpiece, which is an understatement. They are NY--in a nutshell. That's their market. Sure, they finally came out with a Boston version. But they have always been NY, which means they stroke the Yankees and all the other NY teams. If you work for ESPN, you are expected to say nice things about the Yankees, and not so nice things about the Red Sox.
Schil's job is to come up with digs about the Red Sox. Same with Tito. Same with Bobby before he became fair game himself by putting on a Red Sox cap. The same thing, actually, with Gammons when he signed a big contract with ESPN years ago. He had to wear a NY cap--in part. He is now safely back in New England, and has become Red Sox friendly again.