I would actually answer the question seriously and not do anything to make people feel stupid and therefore defensive about circ (which they will have likely done to their kids or had done to themselves or their brothers, partners, etc.). Many, many, many people have simply never heard anything about circ other than that it is necessary, and they have no idea that the foreskin is an integral part of the penis. I don't think you can underestimate the ignorance people in the US have about circ and the foreskin.
Even my own mom, who has been changing my son's diapers since he was born in 2002, had no idea until last month that the infant foreskin is attached to the penis like a fingernail is to the finger and that they have to use a blunt probe to break the adhesions during a circ.
One context the question has come up in for me has been tabling for an intactivist group. My opening response to the question is that the foreskin constitutes half of the erogeneous tissue of the penis, some 10,000 to 20,000 nerve endings, and that circ is not only unnecessary for medical or hygenic reasons but actively detrimental.