His criticisms of leftist activism in the 1990s is that it will always seek to control and exploit technology to implement their ideology so followers of his anti-tech movement should not rely on them. He then rants against 'green anarchy' claiming it is a kind of naive forest worshipping cult that also should not be included in whatever anti-tech movement. It is a small part of his overall manifesto on who you shouldn't trust to join a specific (terrorist) movement and likely came from his time in academia.

It's definitely not the standard fare you would find on those 2 sites you mentioned just a brief 'don't trust these activists they want the philosopher stone for themselves'.