I will gladly do so

Argument analysis:

Explicit Premise:

I've been hearing "you can't be a leftist if you're not against NATO" since Geocities was a thing.

Unstated major premise (laughably false):

There do not exist legitimate critiques against the NATO bloc

Conclusion:

[therefore] Marxist-Leninist groups have been captured by Russian and Chinese state interests for decades.

My response:

Parent commenter absurdly acts as if there is no other explanation, which is ludicrous. Parent comment likely commits "falacy of the missing middle" with the missing premise also being the most obviously false one. The great thing about a reducio is how it cuts through all that noise

Hope this helps