The other day at gymnastics, my husband witnessed my son being pushed by an older boy. He pushed him to the ground twice and then grabbed hold of his nose and shoved him away. My 5 year old son did nothing to retaliate. He simply stood up and waited for his turn on the apparatus. When I asked him about it later and why he had not pushed back, he said "Oh, I don't mind, I just want to be kind." My son is a lovely and kind child and never initiates a fight but when I see other kids pushing him around and he does nothing, it really upsets me. My husband and I are now telling him that he has to push/hit/kick back as and when these things happen. I'm not sure if it's the right thing to do but I don't want him to end up being bullied because he's 'too nice'. A part of the problem is that he's worried about the teacher telling him off. I've told him that I used to get told off when I was little for different things and that it's not the end of the world but it really seems to bother him.
Any ideas/sugggestions as to what I can do/say to him to get him to stand up for himself and, if necessary, fight back?