Block their access to propaganda channels. Don’t tell them you are doing this. Make it look like it’s malfunctioning, if you can. Expose them more to educational material.
Example: Swap fox sub with vox. Set the child lock on their tv. Domain filter facebook in their router or throttle the service to make it unpleasant to use. Set up url redirects. Get them a stack of dvds. Proper entertainment is better than propaganda. They watch that crap cause they are lazy and it’s easy.
If they give up and switches to a more sane channel for their entertainment, politics or otherwise, you have succeeded.
The idea is to remove them from the constant barrage of propaganda from bad actors. If they stop hearing about “evil trans people” every ten minutes, they will probably become uninterested after a while.
Without looking anything up; I would try solving this problem with a browser extention that can hide videos by keyword.
filter FOX, trans, woke and whatever else usually excites or makes them angry. Check their history for a list of things to filter.
If you wanna be extreme, you could redirect youtube to some other video hosting site. you might be able to block some domains to break the yt app but still allow the homepage.
if they are accessing yt through mobile apps, I would consider swapping it for an alternative yt app with the feature of keyword filtering. without checking if they have this feature, you could check out Newpipe, vanced, skytube.
At least you can turn off recommendations and search suggestions and only show subscriptions in the ui.
Do them the service of installing sponsorblock and ublock Origin, to make the browser experience superior to the official app. (also avoids propaganda ads)