I've never been in the situation, but after reading your post, it made me think how I would handle it.
If it were just a single comment with no profanity, I'd let it go. I guess I would step in when the banter took away from the game or became unprofessional. I believe we have a responsibility to handle this. As far as my actions, I'd call the coaches together and let them know that I've heard enough. One more word and the enemy will be shooting FTs.
When I get in a tough spot, I ask myself (not out loud 
)this question. "If there was an evaluator in the stands watching me, what would he/she think about the way I handled this?" In this case, if my partner(s) and I were to let a lot go, I believe we would be marked down for it. Just a thought...