You can't prevent bullying for any particular detail. When a kid wants to make fun of another kid, the details are irrelevant. Bullies are sharks, they will find whatever detail makes someone unusual and relentlessly tease them for it.

What's important isn't making them immune to bullies, but making them the kind of person that people don't want to bully.

But how or what can we do this? I am not father already, but think about how a kid can be bullied because of the parents sexuality freaks me out. Specially because as I fight against  a depression illness, I got totally worried if the kid (s) can, because of the bullying, got depressed too.

What's important isn't making them immune to bullies, but making them the kind of person that people don't want to bully.