Two men, stand side-by-side as they watch an exciting horse race. One is a skinny, slightly nerdy guy with limp wrists and the other guy is a big, very tall fellow. An opera singer warbles, "Love is a many splendored thing..."
As the horses cross the finish line, the little guy is a winner and he jumps up and down with excitement, as the other guy loses.
With joy, the nerd then jumps up and kisses the big guy on the cheek as he embraces him -- earning a really angry look from the sore loser.
The text asks, "When was the last time you kissed a stranger?"
This could be read in either of two ways...either the guy is just a sore loser and/or he's not happy about the male kiss. If it was an attractive woman doing the kissing, his reaction would certainly be different. Still, most of the humor remains in the male-male kiss, not the fact that one's a winner and the other a loser.