We're all imperfect in some way. The quirks of our character are what makes each of us unique. The world would be a lot less interesting if we were all perfect.
But a pet peeve of mine is a common interpretation of bad qualities or behaviour as natural imperfections. It's when someone does something they know is wrong but qualify it with "but that's just me". It's the friend you excuse because "it's just how they are."
Our imperfections make us unique but bad behaviour isn't incurable. It might be who someone is now but that doesn't excuse it. I think for our own personal benefit we should look at which of our behaviours are innocent quirks and which are poor decisions that hurt others. We should also keep others accountable and see these excuses for what they are. Shitty behaviour is shitty behaviour.
Of course, changing any sort of behaviour is a process. But you have to acknowledge it first. And acknowledging it requires being made aware that it's not okay. Once someone's aware, they can change with a conscious and motivated effort. If they refuse to, then that's some valuable info you've gained about that relationship ;)