Manager shockingly disrespectful & rude

This occurred at Fiat/Kia Arnold Clark Aberdeen.

On viewing a car I sat with the sales man and went over some figures, he went to the manager to discuss the part exchange value of my car which I had independently valued at several garages on online all returning around the £11,500 mark, on returning from the manager they quoted me £10,000 say that was £1,000 over what they wanted to pay. I explained the optional extras my car had and that the car I was looking to buy had several scratches, one or two scraped alloys and clay marks in the boot, I felt that warranted a deduction in price. The salesman went back to his manager then after 5 minutes or so the salesman and manager returned and abruptly interrupted mine and my fiancés conversation to scower in my face and tell me he will not sell me a car, the salesman looked embarrassed and shocked as were we, he then walked off as if nothing had happened. The salesman apologised on the managers behalf and hoped us the best with our search for a new car and we less, genuinely disturbed by the customer service of a manager at a professionaly dealership like that. This has put me off ever using Arnald Clark again.