I thought this article was going to be like "YouTube restricted one teenager's access to fitness videos"... but yeah, this is a pretty sane move on YouTube's part.
Human society has always been glorifying certain body types and physical violence all the way back to ancient Greek and very likely way earlier. There is nothing wrong with admiring and chasing after a fitness ideal.
To make a steelman out of this case, I guess we can argue overexposure and extreme promotions of unrealistic ideals can warp impressionable young minds. But even then I disagree that Youtube alone has the moral standard and authority to regulate and censor this. They are a corporation, one of the least moral entities currently around in modern time. They have no right to pick and choose what kids can and cannot watch.
Does this change your view of Youtube's new stance?
Personally, I believe for most people, the algorithm is all of Youtube. It controls what show up on the side bar and on the search page. How many people would go beyond those to find a video? By changing the algorithm, YT can effectively restricting access to certain contents.
Regardless, my point doesn't change. A corporation does not have the standing and should not be allowed to regulate moral matters. They operate on completely different principles and letting them control what a person can and cannot see or hear would not end well.