The victim has the right to say "It's just a bumper", not the offender...
If I were you, I would smile at him and ask for insurance, and say,
"Yeah, it's just a bumper. It won't cost you much... Merry Christmas."
My vehicles have been hit from behind twice in the past.
I let them go as long as there wasn't more damage than surface scratches, and
they apologized and DIDN'T say "It's just a bumper....".