Considering low contact after relative excludes my autistic son

[Stressedoutmummyof3]

Have you ever distanced yourself from a relative after you realise they don't accept your child? SIL has a birthday coming up and today my dad told me that my youngest son wasn't invited. SIL apparently said "if you are planning anything for my birthday x isn't invited."
My eldest got involved in the situation and eventually my niece texted me saying if there was an issue we should have texted her or her dad and if we did have an issue we did have a problem we didn't have to come.
I was thinking well obviously we aren't coming because what do you expect me to do with my autistic 5 year old if he's not invited. I let her know we wouldn't be coming but I actually don't want anything more to do with them.
When I thought about it I realised SIL has never really interacted with DS and not has my niece. My brother is slightly better but not much.
Compared to the rest of the family they don't bother but now they've excluded him I'm thinking why should I bother? Am I unreasonable to go no or at least very low contact with them.
I hope this post makes sense I'm so angry and disappointed.

You are not being unreasonable. They give you nothing - so give them nothing back.

Your not being unreasonable no, I’d do the same

Thank you for responding. I still feel upset this morning, luckily DS is level 3 and doesn't know what's going on but I mean I have kind of expected judgement and exclusion from strangers but from his own family is too much.
Maybe they feel awkward around him but they've known him his whole life. This is their nephew and cousin. I can't imagine my other brother, my sister or their families acting like this. I can't imagine my husband's sister and her family acting like this.
It's shocked and upset me more than I would have thought.

You feel upset because you expected better from them. That's ok - it means you are a lovely person who sees and expects high standards in people and she has let you down

if this happened to me, I'd say she would be dead to me and no longer family - I can be quite brutal in that sense. All or nothing when it comes to love and trust