Fans Upholding the Concept of K/S was a button that some fans wore at conventions (1980s?) to let other fans know of their feelings toward slash, Kirk/Spock specifically.
"... somewhere between the inception (whenever exactly that was) and the 80s development, things somehow got stalled and to my mind sidetracked. Hopefully they are getting unstuck but whereas much gay fiction is read (in this country) with respect, just try saying you write K/S at a con! (In the early days we felt almost as isolated as [male name redacted] at cons as K/S writers/readers, gay or not. I used to wear my "Fans Upholding the Concept of K/S" just above my "How Dare You Presume I'm Heterosexual" badge." 
- ↑ from The K/S Press #23