I am curious how the usual culprits here, the TSA, let him anywhere past security, unless of course, he "chose" not to wear it through security?
A couple of things could have happened. He took it off as part of the normal 'metal objects' process before going through the arch, or the TSA didn't notice what it said (very small AIUI), or the TSA
did notice and read it but did nothing because their 'rules' don't cover the situation.
Crew quite correct to ask for it to be removed if they felt it inappropriate (wouldn't have bothered me), and Capt. also quite correct to turf him for non-cooperation.
Shame really, there are some serious, legitimate (IMO) concerns about security vs. rights, but this kind of publicity does the cause no good at all. Don't know as he's a grade A f***w** though, I'd give him a C.