But if you want to follow that train of thought with that faulty premise, then sure yes we must stop communism to lower prices because the OP says that oligopoly is solely responsible for price increases, so it follows that further restriction on market participants further increases prices. I don't agree with that premise, but if that's your view and the OPs view then it would be logically consistent for you to also advocate stamping out communism to lower prices.
(Also communism doesn't follow the same rules as monopolies.)
They advocated for competition instead of ogliopoly. You decided to talk about a completely different and irrelevant way there could be a lack of competition. Even if your conclusion is right, that they would be against communism if it was a realistic threat here, there was no reason to bring it up.
I could say that a bunch of badly placed volcanos would reduce competition and they must be against those volcanos. Such a statement is technically true but it's a non-sequitur.