First of all I would tell my son on the spot that this is not ok to say and later at home I would try and have some more conversation about it.
There are some nice books out there about inclusion which can help: The Big Umbrella (a sweet extended metaphor uses an umbrella to demonstrate how kindness and inclusion work…A lovely addition to any library collection, for classroom use or for sharing at home) and My Friend Isabelle (Isabelle and Charlie are friends. They both like to draw, dance, read, and play at the park. They both like to eat Cheerios. They both cry if their feelings are hurt. And like most friends, they are also different from each other. Isabelle has Down syndrome. Charlie doesn’t.)

You need to keep reassuring them we should like everyone and even if you don’t like them you still need to be nice to them.

Kids are funny little creatures, you can only are your child with manners and common sense! they like us find thier own place in the world!

Just be careful how you handle your own feelings around your little one. If you immediately react because you are embarrassed you are virtually telling him his own feelings do not count. Giving him the politically correct version of “we have to like everyone” you are setting him up to not be open to you about his feelings when you want him to be. He sounds a lovely little boy and you sound like a wonderful family but at three years old your son needs more growing up time to develop the kind of social skills that you would love him to have. All children are capable of being burdensome to others and the child with special needs is just as capable of causing unhappiness in a classmate as any other child.

Its one of those things he may not be friends with him today but best friends with him tomorrow.

Kids are often not afraid to say what they think at that age.

Kids are not afraid to say how they feel at times, regardless of how embarrassed it makes you feel.

Its best to tackle this problem at home and keep telling him it is not nice to say those kinds of things to others who are a bit different as you would not like it if it were you and try explain this way and keep repeating this he will start to take it in

It’s sad but they all say the ” I don’t like you” which is not nice

I’d talk to your son and find out if there is a reason why he doesn’t like the other child. Something may have happened between them, even a simple misunderstanding.

do they get along when the parents aren’t there?

Just remember kids are allowed to dislike people just like adults

Kids have different best friends each day and take it personally if someone doesn’t share or whatnot, but they come around pretty quickly.

have a chat to him and see why, maybe there was a disagreement between the two. I’d probably think he’s following the lead of other children – unfortunately kids know when someone isn’t on their level and will pick on those who they perceive as “different”. So maybe its a little bit of that? If you see this behaviour continuing, and you think its worthwhile, invite the little boy over for a playdate

Why was he unfriendly? Maybe there has been a problem – I wouldn’t try to make him like everyone – yes he was blunt but at that stage kids are – maybe ask him why he doesn’t like the boy??

I think every kids is like this its just the age he will grow out of it

Sounds very typical of the age. Just keep encouraging him or even putting it to him how might he feel if someone said that to/about him

You should have a conversation with him about how saying certain things makes you feel. Use examples “saying if (so and so) said this to you how would you feel”? All you can do at this age in try and teach them empathy. Its kinda inevitable that situations like this will arise.

I think talk and explain to him if possible through story. I suppose there are children story books in library about friendship and how to make friends explain in children’s way. Sometimes young children said the things like that but not really mean it. My son preschool age said the similar thing like he doesn’t want to make friends with anyone except his cousin.

Cheri J. Meiners does some wonderful kids book about accepting people and other behaviour you may want to look at them either at a bookshop or local library.