This is a quote from Jordan Peterson. I've provided two examples, one in which he qualifies the major viewership as being "young" males, in the other it's a generalised statement about all men. I've heard him make this claim many times, but obviously can't go dig up all the instances.
"Most of the people who watch Youtube happen to be young men"
Link to quote in video
"Youtube is a male domain primarily ..."
Link to quote in video
I've found the following information.
8.YouTube’s male-to-female ratio is about 1:1
Many sources speculate that majority of YouTube users are male, however, studies conducted by Google and Nielsen actually found that the gender demographic is evenly split, with female viewership in the slight majority. While YouTube's total user base might be closer to 50/50, studies have found that men make up the majority of viewers in 90% of YouTube’s content categories. The most male-dominated categories are in gaming, sports, and virtual worlds. Female dominated categories are make-up and cosmetics, skin and nail care, and weight loss.
Mediakix, claiming to be a marketing agency on their site (written March 24, 2017)
An article from from two years earlier gives this information:
While it attracts an even split of women and men, YouTube is still fairly male dominated. Men spend 44 percent more time on the site per month, and of 51 categories of YouTube content measured by OpenSlate, men make up the majority of viewers in 90 percent of them.
The demographics of YouTube, in 5 charts (written April 24, 2015)
Not sure how much things change since 2015 or 2017. A reminder that both quotes made by Peterson were made this year. Those charts from the second source do show that there are some major differences in video subject matter that males and females tend to watch. Also, I don't understand the second source when it says there's an even split of males to females, yet males spend 44% more time on the site per month. Wouldn't spending more time on the site mean you're watching more Youtube videos?
The most recent quote, from HARDtalk, which was said just two months ago in August is the one which claims "most viewers happen to be young men." As a general statement is it reasonable to doubt that more males watch Youtube than females? Also, how about when we add qualifier "young" to males?
Also, I'd like to point that he's mentioned in the past that most watchers of his own channel are male, but I find it nearly impossible for him to have derived the general conclusion from having extrapolated his own channel's data to the whole world. So I wonder where he's got this information.