To be very annoyed at this ungrateful child?

I doubt that this child is autistic; far too readily used as an excuse, and if he had been diagnosed the grandmother would have used this as an explanation.
She should have reproved him and apologised to your grandchild; he won't learn manners otherwise. I am surprised at the numbers of grandmas who tolerate rudeness in their grandchildren that they would never have permitted from their own children.
Up to you whether you continue seeing them.

Shocking behaviour and I think his grandma should have told him he was very rude. Perhaps she talked about it to him when they were on their own but I think she should have also said something at the time.

It's rather sad really because nobody likes a spoilt brat and his family are doing him no favours in letting him behave in that way.

If it were me, I feel sure that my initial reaction would be to steer clear of this lady and her rude grandchild. But as you like her, perhaps that is a bit drastic. I think I might be tempted to comment if he behaves in a similar way while you are in their company. It runs the risk of ending the friendship but I think it would become too irritating having to ignore such rude behaviour.

Exactly Antonia I have on occasion been heard to ask ‘just who do you think you are talking to?’

Agree with OldMeg here, this was such a rude reaction, and not surprised that your DGS was confused. Children should be taught from a young age that it is not acceptable to express dislike of a gift and that they should always respond with thanks. If any of my DGC spoke to me like that they would get short shrift!

I’m afraid I would have said in a loud voice ‘how rude!’

Sounds like a budding Dudley Dursley from the HP books! It a about time his parents and the grandmother woke up and smelled the coffee before the boy gets much older and is beyond redemption. My GS had a friend like this. The way he spoke to his parents - especially his mother - was beyond belief and he was old enough to know that it was unacceptable. Neither DD nor I were sorry when the friendship fizzled out.

This child sounds full of anger. I had a close friend whoe son was the same, he would call her a bitch or a fat cow in front of me and others, she would laugh it off but I could see that she was mortified.
Next time it happens perhaps say something along the lines of " X seems to be a bit unhappy today, has something upset him?" Your friend maybe relieved to have someone to talk to.

Is it possible she thought it better not to make a big thing of it at the time, but gave the little boy a big lecture later?

Even at the age of four this little monster should have been taught that it is very wrong to hurt other people's feelings and sometimes we have to say thank you for things we don't actually like.

I would be angry too, although I wouldn't say anything. I hope my silence would speak volumes.

Sorry, cross post with you Cherry. As far as I know, there are no issues but I will bear it in mind. I'm not sure what to do now in terms of staying in contact with them.

Thank you. I feel quite hurt actually that this woman who I now consider a friend, didn't do more. I know it's hard when it's small children and I always try and think that there might be something else going on to explain certain behaviour. But then I also think that we excuse so much these days when it comes to bad behaviour and this little boy really needed to have been forced to apologise to my dgs and me. What's going to happen to him if he grows up thinking he can treat people like this?

Sorry should read grandson not granddaughter.

Distressing for both you and your granddaughter.
It is possible that the grandson has not been taught kindness and good manners.
And it should have been explained to the little boy that it was not nice way to treat his friend and he should apologise.

However the grandson may have a type of autism
In which case the school will be communicating with the parents.

Your friend may be in an unfortunate position with family loyalties and keeping matters private.

Your poor little grandson.
The other little boy sounds rather angry and unhappy, it seems like a bit more than just bad manners, but like you say, you can't really do anything about it.
I do know how you feel in some ways because one of my Grandaughters' other Grandmother lets her other grandchildren speak to her in the same way that you describe and I too, hope that my Grandaughter will not start doing the same.

I don't think you're being unreasonable. The little boy was rude beyond rude.

Other people's children - who'd 'ave 'em eh?! Not a lot you can do except explain to your DGC that it was a bit rude and that you know he would not do that.

Sounds like a horrid spoilt brat! Manners start at an early age I quite agree with you. Your grandson will have learnt a lesson too.....how not to behave!