>Stopping the conversation with a friendly dismissal, a as you said, is a reasonable reaction.
To clarify, I didn't mean that "chuckle and a reply and off you go" was the means to extricate oneself from such a situation although, as you said, it's a reasonable thing to do.
I meant that an "offhand remark, a chuckle and a reply and off you go" was the whole point of such an interaction -- not some sort of prelude to something beyond that.
Continuing the conversation, and using it as a launching point for something substantial, is a reasonable reaction.
Stopping the conversation with a friendly dismissal, a "chuckle and a reply and off you go" as you said, is a reasonable reaction.
Reacting rudely and thinking "who are you, why are you subjecting me to the labor and chore of talking to you?" is not a reasonable reaction.