Dilberry - I've been thinking about your post and your question about your son. It's such a hard one, isn't it? At one and the same time children desperately want to fit in (humans being social animals) and want to be one of the "in" crowd, and as a parent you want to foster their social instincts, but at the same time, when that "in" crowd is modelling behaviour you're not comfortable with, what do you as a parent do (and at what stage do you step back and start to let your children have more autonomy). And for me as a feminist and a parent, the difficult trick is balancing the fact that, like it or hate it, we live in a society where social acceptance hinges on understanding (though not necessarily conforming to) gender roles, while not buying into the harmful aspects of gender roles and equipping one's children to challenge them or move away from them where appropriate. With a DS (the challenges are different with daughters, because society constructs gender roles differently) most of the issue arise round expression of feelings vs. stiff upper lip, a construction of masculinity built round competition and physical prowess vs. boys who are drawn to quieter, gentler pastimes, and how to help quieter boys form friendship groups when a large part of the social aspect of childhood for boys is built round rough-and-tumble.
My DS is 8 now, and one of the most important things for me has been encouraging him to become a kind and considerate person - I've been a laid back parent (possibly bordering on slack) on a lot of things, but the one thing I have zero tolerance for is unkindness towards others. I think I've also been lucky in that he is a very nice-natured, kind child.
Two things spring to mind, though, in connection with your query. One is not tolerating bad behaviour from others. It struck me in his toddlerdom, one day in a local park when some other boys were trying to exclude him from a piece of play equipment that the flip side of encouraging him to be kind to others was that I had to equip him with strategies for dealing with people who weren't being kind to him, and I couldn't let this sort of behaviour go - I had to be on his side. I adopted the approach recommended by a teacher friend of mine, which is to intervene by asking questions: "Why are you doing this?", "How would you feel if someone did this to you?", "How do you think your mum would feel if she could see you behaving like this?" About 9 times out of 10 this will work. The 10th time you meet an intransigent child, but it's worth remembering that their intransigence is often based on what they've seen modelled at home. So I find I can talk to DS about how some people choose to behave badly, that it gets them a short-term gain but cuts them off from a lot of much nicer, friendlier interactions, and what sort of strategies are available for dealing with people like this (keeping out of their way, talking to the teacher, etc.)
The other thing I've found very helpful is that DS's school has very effective policies about bullying, inclusion and being kind to one another. So for instance, two children choosing to play a game on their own is fine - that's a choice they're making. But when all of the class bar one are choosing to play a game but deliberately excluding that one person - that's not fine. This approach seems to really work - I'm always impressed by how caring and engaged with each other the children seem to be. So it might be worth going into your DS's school and asking what they have by way of policies on inclusion, sharing, joining in games. (DS's school uses a thing called "Kelso's choices" for conflict resolution - a wheel illustrating the things you can do if you've fallen out with someone: walk away, join another game, wait for your temper to cool down, talk to the teacher, tell them to stop, apologize... The emphasis is on giving the children the resources to think about what the appropriate response in a given situation is.)