Although, I don't have a clue why a discussion on free will would warrant that!
It even says so at the bottom of the video -
>> Age-restricted video (based on Community Guidelines)
Creators like myself who may have cursing or other 'adult themes' would need to check a box saying that the content was not intended for children or risk TOS violation. Ergo many people self-imposed age restriction on their content.
So while people are looking at this in the lens of 'YouTube is censoring free thought!' it is entirely possible (maybe even likely) that the creator of the video chose to exclude children from their audience, and that YouTube's request for age verification is the consequence of that creator's choices.
Obviously there are still troubling implications here, but if a creator chooses to age-restrict their own content that's not really YouTube's fault (though their poor review policies combined with a 'shoot first' approach to takedowns could definitely be seen as strong-arming creators into this paradigm).
The age restriction is a separate option, and it's unclear whether the restriction on this Harris/Weinstein is self-imposed or imposed by the platform.
[0] https://support.google.com/youtube/answer/9684541?hl=en&ref_...
You're supposed to be over 41 to understand it.
But see what he just did there? The very thing he said his own kid is too young to hear, he just blurted out. That would mean by his own standards their conversation is inappropriate for children. So perhaps he himself asked Weinstein to age-restrict the video so as not to be a hypocrite.