This Sergeant Major would not have done anything to the kid. Do you think that a seasoned Marine would be riled by a t-shirt? You must have low expectations of them.
The Marines train to kill real enemies, not react to idiots.
"This Sergeant Major would not have done anything to the kid. "
Did you miss the part where the story said he was joining the Marines. I doubt very seriously if the Sergeant Major would be as tolerant of a Marine wearing that shirt as you seem to think.
You're right -- the Sgt. Maj. probably wouldn't do anything. But you can believe the NCO's would....
I had a somewhat similar situation in my unit once with a white Marine putting up racist stuff in his NCO room. Some of the black NCO's complained, the kid was told to take it down, but wouldn't because he claimed a "free speech" right.
Anyway, he came to see me (the XO) one day because he'd apparently been threatened by some other Marines that he'd get the crap beaten out of him if he didn't take it down. He told me the whole story, and asked that we protect him. I told him I didn't see the need for any protection, but that he ought to be really careful walking down the steps from the barracks because he might slip and get badly hurt.
His jaw dropped, and he then went in to talk to the CO. He ratted me out as basically endorsing him getting pummelled. The CO listened, then told him that he agreed with me that the stairs were slippery and that he should be careful. The kid got the message, and that stuff came down.
We don't tolerate that stuff in the Corps, and there are plenty of extra-judicial ways of handling it. A good ass-kicking may be a nice start.