Those are two separate roles, and his answer misses the point,.

Most of the protagonists never have a moment where they consider rejecting good and embracing evil - this storyline has been Rands' own character arc in the last few books, and even then, it never really explored the possibility that he was conflicted about his choice. Egwene, Mat, Perrin and Nynaeve all have grown, but have never veered off the path of the hero.

Petty, spoiled whiners can become villains precisely because of what they are trying to achieve. A cursory glance at any history book can show you that. It is the petty character flaws that drove them to commit their greatest acts of barbarism, and made them turn into villains. Sure they can be Reborn and perhaps start anew, but the point is that the roles they occupy are as a rogues' gallery and villains/villainesses. No one is saying that they occupy the position as the ultimate evil - we are discussing that they fail to elicit the sense of threat that RJ has said he wants us to believe they represent. RJ had a Q&A where he was surprised that readers thought the Darkside was not doing too well and he had to describe the situation as the Light being on its' last legs in a boxing match.