I shall tell you something now that i am deeply ashamed of.
My DP slapped my DD1 (this was years ago) for a very similar thing, she was giving me a load of mouth (she was 15 - relevant, were generally having a hard time with her for lots of reasons) and he said something to her, i can't remember what, and she got in his face and shouted "fuck you" he just lashed out, not hard, but a slap - i think she may have bit her lip, can't remember, there wasn't blood. DP was MORTIFIED and left the house went for a drive i think and didn't come back until DD gone to bed. I was very angry with her of course but horrified at what had happened. Anyway, the next day DP apologised to DD and that was, we thought, it. DP never laid a finger on her before.
DD had a BF at the time and she obviously told him, he told his mum who had sort of taken DD under her wing (fuck knows why!) She actually bought DD a new pair of hair straigteners after i confiscated them because she kept leaving them on, on her bed and going out! multiple warnings, you know the score - anyway - one day DD decided she was leaving home and going to live with this woman, she didn't come home from school, i called her mobile and this woman told me DD was moving in with them and we were abusive parents
We did no more, got in the car and went to get her - DP feeling terrible and that it was all his fault (it wasn't, really) She wouldn't let me see my own DD, it was pissing down with rain, i had a 6 month old DD with me too. I called the police and they insisted that DD couldnt stay there, she was 15 and her BF 18. This woman was vile, kept telling DD not to come home and that she could live with them Police absolutely put his foot down, could see the situation. We were honest with them about what had brought it on. DD came home although stayed with a friend of mine over night, we all met up the next day, talked it over and she came home.
The other woman threatened to call social services so i called them myself, explained the situation (was actually terrified id have my children taken away from me, i was suffering from PND anyway!) They spoke to us all and spoke to DD separately, i just told her to tell them the truth as she saw it and wouldn't discuss anything with her until she spoke to social services as i didn't want to influence anything. Social services were happy that there was no problems, although DD was having some issues as we had just lost my dad, her GF and obviously i had the baby as well, she was 15, doing exams etc so lots going on for her. So they did arrange for DD to have some counselling at school as she struggled with her temper, hence the "fuck you" comment in the first place.
DP should never have slapped her, it was so very wrong, but i think i would have done the same, teenagers just know how to push our buttons and push and push and push.
After that incident, things got better at home, DD sort of grew out of the insolent teenager phase, dumped the idiotic mummy's boy BF and she was much happier. This guy was one of those "emo" types who were fashionably depressed, if that makes sense and DD followed type.
So what i am saying its not the end of the world, it was a parenting fail of course but an understandable one, it may well just let your DS realise how upset that behaviour made you. You need to have a talk to him about how he must not talk to you like that, absolutely not and move on from it. Apologise for slapping him, but expect an apology back from him for the verbal abuse.
FWIW my DD grew out of that horrible snarky phase of her life and is a lovely beautiful young lady now, im very proud of her.