> If an argument is strong enough for a theory, then deniers will eventually loose its steam ( flat earth is going nowhere).

I wouldn't be so sure about that. Crystal ball fortune telling, horoscopes etc. are still alive and well, as is denying the Moon landing and (this will get me downvoted to hell) religion - the most popular one of these.

But going back to the main discussion, these people want to believe something against all evidence (for various psychological reasons) -> more and better evidence threatens their world view (and in the case of YT - revenue stream) -> they make even larger leaps of logic to , start getting more extreme, more aggressive -> their followers do as well. Sprinkle on some echo-chamber effects and you've got yourself a perfect machine for turning "sceptics" into extremists.

Now, with most political issues, conspiracy theories and other beliefs, it doesn't matter much and doing anything against them would be setting a dangerous precedent, but things like this are just too dangerous. We can "debate" the Moon landing for hundreds of years, but climate change is already happening and we need to do things now, not in 1 year or 100. There's no time to hope these people will just go away eventually.