The entire discussion about the war on male agency is interesting, but we're diverging from the original question: why do quality men from rationalist circles, fully aware of the intersexual dynamics and capable of raising politically incorrect points, fall for the poly(andric) trap and advocate for it?
(Quality Poly Men: if you're reading this, please be aware that I deeply respect you both as individuals and intellectuals, I'm just really curious about the genuine/implicit motivations involved in this particular context, and your public coverage of the topic makes me feel entitled to discuss it)
The best explanation so far is: "0.4 gf + some humiliation associated with the vibe of male submissiveness/cuckoldry > no gf, plus even if we were a mono couple, she would quickly cheat on me or branch swing on the current dating market, so I need to get rid of jealousy and mate guarding anyway". It still doesn't explain the public advocacy of polyamory or picking a better relationship model (committed monogamy or nonformalized polygyny).
How about the similarities with the case of Neil Strauss? After his crazy PUA years and recovering from the sex addiction, he embraced the "Purple Pill" perspective, explored polyamory, married a model and had a child. Guess who filed for divorce in 2018?