Stewart seems to have replaced his Star Fleet badge with a safety pin after a series of tweets that began following the Brexit vote in June. The symbolic pin spread to the the U.S. after Donald Trump was elected president on Tuesday.
The pins aren’t holding together a rip, they’re making a statement .. and not a anything out of out of Star Trek.
The pin is what comes after running out of different colors for 
symbolic ribbons.
This “safety” pin indicates that the person wearing the pin is safe for those in danger, whether that’s due to their religion, nationality or other status.