My friend asked her 5-year-old who he'd like to invite to his party from reception class. He replied "everyone except X because I don't like him". So my friend invited everyone except X.
Then she told me what she had done and said, "I'm sure X and his mum won't find out about it". There is nothing particularly difficult about X and his behaviour.
Surely the probability that X's mum never found out is zero? Isn't my friend now lining herself up to have an enemy for the next 7 years, plus possibly to have caused misery to a 5-year-old?
In a similar incident last October, a mum sent round a generous invitation list for her son's birthday. At the time, the son was "too naughty" and not much liked. Quite a few people declined on the ground that their child didn't like the birthday boy. My friend and I both told our unwilling sons that they were going but didn't have to play with him. They went, we made friends with the mum, the birthday boy now behaves much better and 8 months later is friends with both our sons.
I think it is important to avoid singling out and ostracising a child who is 4 years old - firstly because it's immoral, secondly because children change quickly at that age and thirdly for the practical reason that you are committed to spending the next 7 years in the company of his mum! what do others think?
I know you can go too far the other way. A boy in my son's friendship group was annoying the others and they ostracised him, causing his mum a lot of pain. At first, I made the big mistake of just insisting that my son play with him. Then my son became very upset and explained how the boy physically hurts him. It turned out that the boy hadn't really developed his sense of "boundaries" and hadn't realised that hugs can be unwanted, kisses can block someone's mouth and bear hugs can hurt. Once I realised this, I told my son it was ok to say "no, don't touch me!" and that it was his choice whether to be touched or not. He looked so relieved! I also told the mum, because she was pretty upset and worried by this point. She taught her boy to do "high 5s" instead and practised gentle hugs at home - and peace broke out.