If the meaning you (incorrectly) infer is offensive, you might have a hard time asking... Consider this: what if the person who took offense was gay, was recently harassed at a past workplace, was sensitive about the issue, maybe wasn't a native English speaker, and was told by an older coworker that he would play "the straight man" to his team pitch.

And even then, consider that the offended person replied "say what!?" and in turn the older coworker didn't understand the reaction.

Talking to people is hard. Maybe funny metaphors shouldn't be used unless you know the other person's sense of humor. By the way "playing the straight man" while listening to another person's technical plan for a feature doesn't really parse for me; it sounds like a clumsy use of a figure of speech. I'd be surprised too by this usage.