That badge seems pretty unprofessional to me. I would discipline my employees for that sort of behavior, especially if it occurred at my own conference.
Meh...I wouldn't. It's definitely an ingroup-humor signaling thing, but I find it hard to believe that someone would read that and seriously get offended unless they're being self-righteous.
But not nearly as furious as I'd be had it actually read "I reject red hat patches" as claimed above.