More than once I've caught myself leaning into or at least not challenging views that I strongly disagree with when talking to someone espousing them, because I felt it would not really be helpful/productive. I can see Peterson doing the same, and avoiding outright condemning the 'alt-right' in the way you desire because he might feel it would not lead to a desirable outcome.
I'm uncomfortable giving him this leeway, but I have to admit that I respect Scott enough to not write what he did without a decent degree of thought.
For myself, at least, I can't tell if this is the right approach. But at the very least I can say it's not as simple as always expressing my 'true' beliefs. That would be lazy.
As GP points out he's not so critical of his alt-right cheerleaders. Perhaps we would like it if he took some responsibility for his more regressive fans but I don't think he sees that as his problem. Maybe that's fair enough too. Maybe he just sees himself as a guy who's "speaking the truth" moreso than "a leader".