I would teach my son "mean people are mean and that isn't because of anything about you". My son has long hair. He was about 2 when he asked me why he has to cut his hair and I don't. I had no good explanation so I simply told him he doesn't have to either. After that he didn't. He loved his long hair, until one day some very mean children were mean about it. That is all it took. It was one time. He was 6. Two weeks later he tells me he wants it cut and I stalled, hoping to reassert he should love what he loves, etc. He told me since it was his hair, he should be able to wear it however he wants, since I always said that and if he wanted it cut, I should stop trying to talk him out of it. Again, I agreed, and we went to have it cut.
Before having it cut, I gave him the "mean people are mean" talk several times (maybe even a dozen), but he insisted that he was in charge of his hair and wanted this, so we did it. The very firsyt person he saw after the cut was a "mean kid", and he proudly went and showed him his new hair (which was super cute and very trendy - something most kids that age would love) and the first thing that happened is the mean kid insulted the new haircut.
I hated that it happened. I hurt for him. I also look back now and see it had to happen. It was a very important lesson and 4 years later I have never once again seen him attempt to change anything he does to try to please someone else. Immediately he said to me that I was right, that hair was never the reason he was treated badly.
He only got it cut that once, and then immediately started on growing it back out. He gets mistaken as a girl often, because long haired boys are unusual here. The last time it happened with a sales person, he didn't bother to correct her (he usually does) and after I asked him why he didn't just tell her. He told me it's because it doesn't matter, he doesn't know her, so why waste time since it really isn't an issue. He then said something very sweet and told me that most of his favorite people are girls, like me (mom) and that if anyone ever tells him he "throws like a girl" he will say "Thanks, my mom taught me and she has a great pitching arm".
The point of all that is, within my family I work very hard to constantly tell my kids we are a team. We support and encourage one another to be who we are meant to be, with all our quirks and characteristics. We build one another up and have one another's back. We are never ever to be the source of emotional pain for one another. We are never to criticize things that are simply differences, not only within our family, but to others. And in the end, teaching your children how to support one another, and supporting your children is the best way to prepare them for a rough world. The world will always be a difficult place to navigate for young people but if home is good, solid, safe, builds them up, etc, then it will be a far more manageable world because they know they have people in their corner who love them just as they are.