My child copied his autistic classmate's stimming actions

My child is 3 years old and does not have any development issues. Lately he has been showing stimming actions like shaking of hands, tapping of fingers. I asked him why he does that and he said because his classmate (who is autistic) does that when he is happy. I told him firmly to stop doing that but he usually would laugh it off saying because he wanna be same as his friend. Should I just let him be? #advicepls