All you need to say to people like that, is, "I didn't buy it for you, I bought it for me." That should end the conversation, and it will if you just turn and walk away.
They will even ask why you didn't buy a real Harley if you are riding a Harley. I rode 1200 cc Harley Sportsters for around 3 decades. The dealships would ask when I was going to buy a real Harley when I went in there for parts. People who could accually tell the difference in a Sportster and the big twins would ask me the same thing. If they were serious about it, I would tell them how much lighter and easier to handle the Sportster was. Not much difference in acceleration either. Being several hundred pounds lighter, maybe more if the big twin is fitted out with full saddlebags, fairings, and windshield, the difference in weight and wind resistance would put the Sportster ahead in a sprint. You can blame part of that on the dealerships, because they want to sell you a model that costs twice as much new. The salesman will try to tell you the Sportsters are the starter models and everybody moves up the big twins. I proved them wrong on that.