>All bullying is based on traits that set you apart.

This is certainly true. What I meant to convey was that in the context of a programming class, being bullied for a trait that is itself already suspect within oneself reenforces it and thus is more damaging. If that girl had been bullied in the programming class because she was fat, it may not have had as much of an impact on her decision to pursue the career. Being bullied because she's a girl on the other hand, had the secondary effect of reenforcing the idea that she doesn't belong in tech.