One of the signs of the khawarij is they obsess over the faults of others–it’s all they see. They never see their own faults. One of the signs of the awliya’ is they are constantly preoccupied with their own faults, which seem endless. They hardly have time to see the fault of others, their schedule is filled to the brim with their own and with ‘ibada.
When you see the fault of another, realize first that you are likely seeing your own fault, or an aspect of it. It’s just that their fault has become manifest while yours is hidden–after all, Allah is الستير as-Sitteer, the Concealer.