Agree this is the downside to gaming I've seen / heard it for myself with dd 14, who started getting into it during lockdown. Friends suddenly have the bravado to say horrible things in the heat of the moment that they wouldn't say to your face in person.
I'd definitely address it with the parents if you know them, thing is kids love to call someone a snitch and it just causes more issues for the child say if you were to tell them ds came to you upset and told you what these boys said. Personally I'd protect him from that by saying you were in the room / just outside, and heard them say something along those lines, please could the parents address it.
Saying that, if that kind of comment or attitude comes from the parent or within the family itself, then sadly there's not a lot you can do other than distance
yourselves from people like that. Dd is ND but to the outside world "high functioning", if I got the feeling that kind of ignorant attitude came from the family at that age I would keep her away from the kids as much as possible, we don't need crap or people like that in our lives and time to protect and be selective over friends.
It could be a one off, but in case it isn't or it spreads to others, ds should perhaps be armed with what dd calls a comeback. Ask ds to tell you if it happens again, if it does or happens at football now as a repeat comment I'd address it through the football club, hopefully they'd take it very seriously.
As an aside, I remember a couple of years ago finding out from dd and her friends, that saying someone is autistic is used as a slur, basically like when I was young and kids called someone a s***c, just horrible and ignorant.