[sima_yi]

... belied their utter intellectual impotence...

The word belie means to give a false impression, or to demonstrate the falsity of. I think the author means "...demonstrated their intellectual impotence...".

[dignitasnews]

It is also to misrepresent. The use of name-calling belies their intellectual failings. “His trembling hands belied his calm voice.”

[abclily]

Yes, I was thinking “...revealed their intellectual impotence...”