Yes. Absolutely.
Among other things, it's very important that your son sees you speaking up like you would if he said it. Consistency is so important. You don't want to send him mixed messages. That gets confusing.
I always enforce our house rules when friends are over. Simply and clearly, but without drama. something like, "That's not nice. We don't make fun of people in our house."
I'd expect other parents to do the same if my kids behaved I appropriately at their houses. I'd never fault another parent for being too strict (or kind!) in their house. It takes a village.
