Hilchos Lashon Hara chapter 4, section 9

Some people have bad character traits – for example, they are arrogant or get angry easily. Even if we see they are used to these traits and do not feel bad about them, it is forbidden to speak badly about them for having these traits.

Many people do not think of such traits as forbidden, and do not know how serious they are. Perhaps this person is the same. If they knew how serious it is, they would try with all their strength not to act this way.

On the contrary: if a person sees that someone is used to bad traits, they should rebuke them and explain how serious these traits are. By doing this, they keep the positive commandment "You shall surely rebuke your fellow." Perhaps the person will then admit they are doing wrong. But right now, they think their way is fine. So it is forbidden to go and talk about them.