I think Sherman was more frustrated with something him and his young teammates are just noticing and that is if you play here, it is easy to overlook what you are doing. He and Bruce Irvin both mentioned the "Pretender" label the NFLN guys put on them. You hear it in his KIRO aftergame interview.
He was venting and showing his disgust with the national perception of things. Deep down, he and Doug Baldwin know that they lost some money due to perceptions coming out of College. You have a team of mid-round talent that have a chip on their shoulders. This year and last, our 1st rounders were laughed at as reaches, so it isn't like they don't feel the brush off either. The only true Blue bloods on this team without question are Earl and Russell Okung. All the others have a stigma to overcome. Leon Washington, Michael Robinson, Mebane, Red, Clemons, Branch. The list goes on and on.
He probably cooled down from the emotions of the game and took down the "U Mad Bro" pic. But it is too late as that has already spread like wildfire. NEP will use it to motivate themselves for the Jets and dismiss his tweets as a sore winner, since they wouldn't understand what his deal is. Figure he is just a loud mouth. I have already seen some of the national guys shocked that Sherman would speak of Brady in such light. Doesn't he know that Tom Brady has won multiple SBs and was league MVP? You know, the usual elitist view of things.