That was insensitive and rude. Would they sit around saying that they would never want to have blonde hair or brown hair?
I think if you didn't have the energy to enter that conversation then that is fine I understand that but I would have probably said, I love my curly hair, I don't have to fry it with a curling iron to get my curls like so many people do, and I can flat iron it if I want to, my hair is versatile and I would hate to have straight boring hair all the time. I wouldn't have been able to keep my mouth shut but that's just me.
I'm really glad that I have always been around people who loved my curly hair even when I didn't. My friends and family have always encouraged me to wear my hair curly and told me that it was beautiful. Many people I meet always tell me they wish they had curly hair too and I have grown to accept my curls and love them. You can't make people less ignorant by force but you can do what ever possible to make sure your daughter never thinks like them.