Kids come with different personalities right out of the box, ask anyone with more than one kid. You've bought into some liberal propaganda that people are fully malleable objects. We are not. It is a combination between nature and nurture. I personally believe it is significantly more "nature" in this case.

There are certain aspects of your personality, like "arrogance", that the society might find unacceptable. That doesn't mean that they are bad for you or that you can change them.

People are pretty malleable though, is the thing. We like to think otherwise because it’s cognitively simple to think people (and ourselves) are static objects as identities that don’t change over time. In fact, people are very dynamic and change dramatically over time in response to their environment, self-inflicted or not. It can be anything from sudden trauma causing drastic personality changes, puberty, or rigorous work at changing one’s maladaptive thinking patterns.

Of course they are bad: you will be shunned by peers, you will have stunted communication skills. Interpersonal relations and communication is a critical skill for any endeavor where you don't work alone (I've no idea what is it that you do).