What the hell just happened?

I had the cable company send some one out to fix my Wifi connection. The cord was chewed up by my 7 mo old puppy. He came, we had a nice conversation, he fixed the cord, and was headed on his way. At the door, he told me to have a nice day. I replied with "thank you, sir, you have a nice one as well!". He immediately became offended and started scolding me. He said "that was very rude." Confused, I asked "um... For saying 'have a nice day as well?'" He said "no, for calling me sir. That's just incredibly rude." I apologized, but he just stormed back to his truck shaking his head. Can someone please tell me what I did wrong, if anything? Because part of me wants to call and complain about his lack of people skills, seeing as how I was just trying to be respectful and appreciative of his service...