The funny thing is without Sherman, the entire narrative of the SB would be about Manning.
Sherman got the floodlights on this defense. Now we are the bullies. We wear the black hat, which is always great theater.
As far as whether it was necessary? Of course it was!
Almost anyone familiar with this team is aware that Earl Thomas might be more important than Sherman, but absolutely nobody talks about him (except during games whether the announcers acknowledge his ability/importance). Yet Sherman screaming in people's face? That gets everyone to acknowledge he is the best. Because the visibility creates a perception of importance.
Sherman looked right at the camera. It might be a bit selfish but it is clearly orchestrated at least by him. He is playing the heel, we get to be the Evil Empire and consequently the interest in this SB is going to rise. Also, this is going to take some of the pressure off some of our guys IF they can avoid resenting Sherman for sucking up so much of the media attention or becoming the center of attention.
Sherman is playing a character that represents what our defense is about, and this team is going to be sold/marketed as the Defense in a Offense vs Defense storyline.