OK, I have known a similar situation , and this is my suggestion, as you are mother / granny.
firstly check it's not because of a much loved aunt of baby's father!
Quietly say something like:
I think this is a lovely name, but I just want to check that you have listened to the words of the song and know the Biblical story it's based on.
The 'pop culture'reference is quite an enduring one, especially as it's sung as a football song (can't remember which team) and they have been asked to stop using it because of its violent lyrics. You might even be able to bring that up, saying 'well, I hadn't quite realised, but this team have been asked to stop singing it.....'
By saying you personally like the name, you have pre-empted the idea that you are interfering.
It is astonishing to me how so many people just don't listen to song lyrics: the situation I was on the fringe of, I said to a friend of the parents 'have they listened to the song?' He said ' they say they have, but they only really know the hook - I'm going to make sure they listen to it all'. They did, and changed their minds. That was another pop song, but one that has endured a long time.
They can always use it as a middle name, so the little girl can use it when she's older.
I am also assuming that dad is conversant with British popular culture. For instance, for a long time, very few girls in Britain were called Lolita or its variants, but that didn't extend to Spanish / Latin culture.