I get your point, Claires, I do. But I think there's a big leap between burning books which already exist, and two well-loved British comics writing something which was going to air at prime time on Christmas Day when half the country would be watching, and presumably not even thinking about the fact that it would hurt some people. I saw a great Tweet that said all that scene needed to redeem it was Nessa saying over that line, "oh, I don't feel comfortable with that word you know" - and it's true. That would have been kind of funny (Nessa, bolshy as hell, subverting her selfish/gives no fucks persona and being a bit 'woke') and given the tiniest nod that says, yep this song is part of British Christmas culture whether we like it or not, but it's okay to acknowledge that part of it it harmful.
Now, there are a LOT of gross things in Gavin and Stacey - fat jokes, slut jokes, all sorts - that I personally think are pretty horrible, and I haven't watched it since I was about 18 and grew up a bit. But those episodes, like everything else you mentioned - plays, books etc - are already out there. What we should be able to do is to show that we've evolved and learned and that what people thought was acceptable five or ten or fifty years ago isn't necessarily okay now, and change accordingly. It's not a big ask.