How is wearing a collar a form of humiliation? I can imagine that wearing a collar I didn't want, from someone I don't respect, would be humiliating, but I don't think that's what you were talking about.
If I accept someone as my mistress/master and wear their collar willingly, that's not humiliating in the least. It's a physical proof that I'm accepted and valued by someone who I deeply cherish. That's like the opposite of humiliation. I would be proud to wear a collar like that.