Earlier quoted context omitted.
Refusing to acknowledge the affect of hurtful words on yourself, is pretty much the opposite of "proper habits of the mind". Denial does not make healthy people.
It's not denial so much as it is not caring to the point where you get upset. I think that's the strength of mind that GP is referring to.
Part of living is opening yourself up to people. That includes the risk of getting hurt. That's normal and part of the human experience.