Bookeatingboy
FFS, just go ask the parents.
This is ridiculous. You know, it's possible to lightly and skillfully navigate social relationships while occasionally broaching sensitive topics. Adults do it all the time. On MN, people act like you only have two choices: screaming at people in an incoherent rage OR letting things fester until every relationship is poisoned.
This is what I mean about being bitter. Your son has SN but is one of the most popular kids in school and has great relationships and friends. Plenty of NT kids don't even have that! I know exactly what you mean about mixed race boys being cool btw and I understand that it probably means the older boys acknowledge him and he is "known" in the school. Girls will likely be all over him as he gets older so get ready for that. So you have a kid who is cool, happy, has friends and is well liked - and will probably get tons of female attention.
Yet in this one instance, you immediately jump to him being SN as the problem and it's clearly completely poisoned your view of all of these parents that you don't know.
Most of the SN parents encouraging you are describing situations completely different to yours. They are talking about their kids experiences - who have no friends and have a terrible time at school. You are in a completely different situation to them. Honestly, if you go into this with a big chip on your shoulder and a barely concealed determination to see the worst in everyone, you will likely do more damage to your son's future.
It's obvious that you can't privately let this go, so just ask. Politely, respectfully and lightly. You can a lot tell from body language so watch it, get the info you need and move on. This is a perfectly socially acceptable action.
Whatever you do, don't NOT say anything because you are "bigger person" then try to "forget about it" but let the suppressed anger and hurt seep into every single future conversation then be shocked - SHOCKED - that these relationships now seem awkward and tense. Then run to MN and post about how other parents are so awkward and it's probably because they are so prejudiced about your son's SN.