I made a similar point a while ago (maybe last year) and there were some pretty good objections to it. Unfortunately I couldn't find that post when I looked for it last night!
One obvious counterpoint is that using AI tools allows manipulation of the discussion in a similar way to using a bullhorn in a coffee shop, only without revealing that you're the one holding the bullhorn. 10,000 bots "contributing to the discourse" in accordance with prompts and parameters controlled by one or a few individuals is quite different from the genuine opinions of 10,000 actual humans, especially if anyone is trying to use the discussion to get a sense of what humans actually think.
Edit: More correctly, they'll be making contributions to the discourse that closely mimic the human distribution, so from a pure content perspective they won't be making the discourse any worse in the very short term.