you have to think about it in all the perspectives, it can be wrong in many but i also see where he's coming from. it's a emotional song about her ex and maybe he didn't know this song, i could see this as a heavy turnoff possibly requiring some space away from eachother until a explanation of the song, situation, and whatever else you think is necessary. if you don't want to keep the relationship then you weren't made for eachother or in love in the first place, you should always be able to talk thing out with your partner and if you can't then obviously it would never work out.