Hypothesis: The psychology behind the turmoil caused by the red guards might be very related to contemporary phenomena in academic settings and on social media, where the rhetoric of social justice is perverted and turned into a weapon to antagonize anyone in the perceived out-group. (Of course, the magnitudes of the resulting problems are vastly different.)
Group dynamics can result in some awful things. It's expressed anywhere from kindergarten, highschool to politics, online bullying, conspiracy theories, etc. So, yeah, they have things in common, but as you say, the outcome in China was grievous and devastating.
Thankfully accounts still survive and if I recall correctly, there have been a couple of Chinese movies which broach the subject, although not certain if done in Hong Kong.