I will present the argument that despite the specific instance being two straight males, the joke would apply to the scenario of kissing anyone that you don't really want to. Examples: ugly person, someone you dislike, gay kissing opposite gender. You could even get racist with it if you like. It's funny to kiss someone you're not attracted to to win a dumb competition. The era the movie was made was definitely more openly homophobic, but two straight dudes being perfectly fine with making out with each other is definitely not homophobic, and is actually supportive of not making a big deal out of two men kissing. Also, the characters that show disgust are presented as not likable people.