I think Sherman's wrong here. Firstly, I've no doubt Rhule discussed with Raiola about talking to the press and either asked him if he wanted to participate or, more likely, explaine why he wasn't going to participate.
Secondly, denying Raiola more time than the other QBs or even other freshmen, shows he's not giving preferential treatment to any one player, no matter their potential. Everyone's on an even par, particularly in the QB room.
[Edit: I don't think Sherman is concerned about giving Raiola "practice" in front of a microphone. I think he wants soundbites.]