I dunno, I don’t exactly get that message from this picture. It looks more like he is doing what others do, and eventually get yelled out for - failing to stand. He looks to leisurely to be accused of doing it to convey a message. Of course, we would have had to have been there to know for sure.
To my thinking, and I freely admit that I could be wrong, is that if he were protesting 1) His head would be held high and 2) he might have his fist clenched above his head.
You don’t kneel for taps.