What an absolutely wretched and thoughtless thing to say to a complete stranger! Saying it to anybody is bad enough, but to somebody you don't even know, and in front of so many others as well... cheeky little ass. I'd have gone nuclear, to be perfectly honest. I could never sit there and allow somebody to question my loyalty to my partner, or imply my child possibly wasn't his; especially not over something like the color of the baby's hair! I generally try to be polite to other people, but that is absolutely unacceptable behavior, and I'd have made certain he knew it.