Many young content creators have comments disabled (or by parental decree) so they don't have to experience intentionally hurtful or negative trolling some comment sections are well known in spawning.
Some other reasons:
I find it irresponsible on Youtube's part, to maintain a commenting platform with such a tremendous budget, and yet without meaningful discussion moderation tools that could be found on much lower-end platforms. These tools are a minimum bar for basically not promoting abusive behavior.
Also, disabling comments helps me to communicate that they are not a channel I monitor for feedback or questions. I just don't have the time to monitor them, and in Youtube's case this means I either have a potential commenting cesspool on my hands or no comments at all.
To some people this is a huge red flag maybe, but I would wonder if they really understand what it's like to be a publisher on the platform. Again and again I have seen good channels derailed by the absolutely broken commenter-publisher feedback loop...
It is not in the interests of almost any site or platform operator to limit drama, trolling, etc. They want the page views, the time spent in-app/on site, the emotional energy and investment.
Look at celebrities. The job of their publicists is to negotiate with other publicists to manufacture some inconsequential tiff that puts the names of their clients in the media.
You picked no discussion. So now nobody learns anything new from eachother and you turned YouTube into a TV channel with one way communication.
But you drop "censorship" front and center about some random dude's YouTube channel and you're doing some sterling fearmongering throughout the thread in general so I'm going to be honest, I gotta think this is less about any sort of freedom to speech and rather about the privilege of being granted time on somebody else's soapbox--the demand to listened to.
Get your own.