Stan's immediate (and unfortunately homophobic) reaction to Kyle coming out to him is "I'm not into guys", "do you like me?!", "did you ever look at me in the locker room?", etc.

+ Points for Kenny and/or Cartman to be on the LGBT scale somewhere.

(OP is a personal fan of Kyman, so if anon wants to add another bad reaction of "you're with Cartman?!" OP would love the added angst.)