What would you do?

My son was at the park yesterday and he was playing on the play equipment and he comes up to me crying saying nobody wants to be his friend. He's an only child who happens to have Autism, so social interaction is sometimes hard for him but he wants friends so bad. After I calm him down and we play tag on the field he then tells me one of the kids said bad words to him, but he didnt say what.

My question is, lets say you heard the kid saying bad words to your kid, how do you address that? Also, I constantly hear f- bombs from children on the play ground, and cussing in general. From my assumption, a lot of the kids's parents may not have english as their first language, we have a lot of migrant farm workers in our town, so there would definitely be a language barrier for me and also they may not be completely aware of what their child is saying.

It was so heartbreaking to see him get upset. I'm just wondering what I could do or say next time.