The shows that get on-screen warnings for non-PC content seem pretty random too. I've mentioned that the UK channel currently showing Dukes includes a warning at the start, but I don't think they include one with CHiPs, which is from the same era. Another of their shows, an innocuous British sitcom from the late-80s/early-90s, also gets a warning (I'll have to see it again to check the message). The show is based around a man in his 50s dating someone half his age, but I can't see what content might be offensive.
I'm considered old-fashioned these days because I'm still adding to my DVD collection, but at least the choice of which shows will or won't be seen in my house rests entirely with me!