My issue with this specific argument is how long would it take word to spread of a pool acting maliciously? How long would it then take word to spread far enough to significantly impact their hashrate? Lastly, how long would it take someone with 51% hashrate to do damage to Bitcoins reputation or worse?
My issue with mostly the whole argument is what benefit would a malicious actor have? What kind of a bogeyman is being painted on the wall here?
To gather at least 51% of the global hashrate means an investment of billions of $$$ or convincing a huge amount of individual miners to join your pool. Attractive conditions for external miners don't come for free.
What can you do with your hashrate majority? Well, you can double spend your own transactions, you can censor foreign transactions and in essence you will disrupt the coin ecosystem. Particularly the latter won't be for your own benefit, on the contrary! Game theory is against a malicious actor who wants to exploit his hashrate majority. So, what's the fuss about it, unless a malicious actor doesn't care to burn billions of $$$.
I believe this scenario is highly unlikely and an economic suicide, thus the probability of such a malicious investment is neglectable.
Systematic double spends won't go unrecognized, nor would an increase in chain forks due to block races go unnoticed.
https://fork.observer/ is a thing...