I don't know. I have a pretty big mouth when someone is being callous, whether it's a stranger, a good friend or a family member. I'd have said, "That has to be one of the single rudest and dumbest things I've ever heard." Then walked away.
Sure, this bluntness can be rude in and of itself, but it sure does nip things in the bud and usually makes that person think before they speak to me in the future.
Something a little similar happened years ago when I was already in WDW with friends. It was around the time that they had first started offering DVC. Out of curiousity, I sat and chatted with a rep for a little while.
After the chat was over, a friend had asked what I had been up to. When I told her, she said, "Why would anyone want to spend that kind of money for a place like this? Anyone who would even consider it is stupid." (This was a habit of hers since I had known her)
My reaction without batting an eye? "You don't even realize that you just insulted me and called me stupid. THINK about what you're going to say before you open your mouth next time."
She was floored and stomped off in a pouting huff but to date, many years later, she's never ever said anything remotely like it to me again.