perjorative: (n) a word expressing contempt or disapproval.
I also considered that other commenters might not think using "gay" as a perjorative was a big deal, but HN rules encourage the assumption of good intent.
From the article: "The college I attended was small and very LGBT friendly. One day someone came to visit and used the word “gay” as a pejorative, as was common in the early 2000s. A current student looked at the visitor and flatly said, “we don’t do that here.” The guest started getting defensive and explaining that they weren’t homophobic and didn’t mean anything by it. The student replied, “I’m sure that’s true, but all you need to know is we don’t do that here.” The interaction ended at that point, and everyone moved on to different topics. “We don’t do that here” was a polite but firm way to educate the newcomer about our culture."