This was an interesting challenge. Here's my attempt: "Merry Christmas."

The more PC term is "Happy Holidays", but I'm not so sure "Merry Christmas" is offensive contextually -- at least, not always.

Most of the actual conflicts that get reported as people being "offended" by "Christmas cheer" or similar involve legal challenges against government entities endorsing or privileging a religious interpretation of Christmas, such as local governments dedicating public space exclusively to a nativity scene. This sort of thing is a pretty blatant Establishment Clause violation. This then gets spun by right-wing media as a "War on Christmas" waged by liberals who hate Christianity, which then turns into parts of their audience believing that saying "Merry Christmas" as a private citizen is somehow a noble act of defiance.

I think this does not answer the question. I don't think "Merry Christmas" or "Holidays" is the type of example @iovrthoughtthis is looking for.

I'm also not sure those are the type of "PC" that was meant initially.

Though I could be wrong. Does HN get up in arms when people say Merry Christmas?