This is one of those occasions where your husband is learning something in college that isn't on the syllabus.
He should not only go, he should go cheerfully. He should dress up. Bring something nice to share, bring a hostess gift and bring his own - higher quality "footies". He needs to set himself apart.
Like you said, he isn't a beleaguered "college student". He is a man in his 50's. He is a man-o-f-the-world. He should know, by now, how to rise to the occasion, especially when it is an unreasonable "boss" making the demand.