Peterson is definitely a gateway drug. There's a gradual progression from "conservative left-wing" (e.g. Carl Benjamin, who for a long time self-identified as "left-wing"), "anti-SJW"/antifeminists and centrists to the alt-right and actual nazis.
I'm sure Peterson sees himself as a conservative and a moderate, just as I'm certain Carl Benjamin used to think of himself as "actually a leftist". But the "moderates" and "centrists" obsession with "SJWs" has shifted the Overton window and some former alt-right creators have recognised this and since reoriented themselves.
Peterson and Harris are useful figureheads because they register as moderates or centrists if not liberals in most people's minds, but they're extremely close to conspiracy nuts like Paul Joseph Watson, race realists like Stefan Molyneux, or people like Ben Shapiro.
I used to watch a lot of YouTube "skeptics" (mostly former YouTube atheists who left that movement over the "Atheism+" debate) and I experienced the progression first-hand, with anti-SJW panic, Buzzfeed obsession and other nonsense resulting in self-described centrists aligning themselves with the right by seeking out the more presentable right-wing extremists (and maybe a few center-left moderates "for balance"). Quickly there were videos about race realism, white genocide, and even "the Jewish question".
Luckily I managed to jump off that train but it wouldn't have take much to nudge me over that "centrist" stop gap (especially with Peterson and Damore normalising the rational disconnect I experienced).
Also it's worth mentioning that even at my most "centrist" I never got as much hate online from "SJWs" for incredibly dumb statements as I got from "liberals" as I shifted back to the left. Leftists just blocked me. "Liberals" trolled me, downvoted me and drowned me out with vapid memes (all in the name of "free speech").
EDIT: Case in point, here's YouTube atheist CultOfDusty who joined the alt-right until he realised that put him in the company of people supporting Mike Pence, who stood against everything he believed in. Note that he's still "anti-SJW" but other YT atheists don't make that distinction and have since tried to slander him by taking him out of context or putting words in his mouth: https://www.youtube.com/watch?v=thliETccJss