Agreed, and before terminating an account above some threshold size (say top 5%) there should be a human review or confirmation. But this is not surprising or even unexpected behaviour from YouTube. There are loads of horror stories from users who get their account shut down for 'minor' or accidental infractions. If a user is going to rely on a service with a history of unsympathetic and unpredictable enforcement then they should always take the most cautious approach when uploading.

Which is why a user who relies on YouTube so much should be taking the most conservative interpretation of the rules possible. There are several pages (reachable from the upload wizard) that talk about what may or may not constitute age-restricted content. Implied sexuality is on that list and if the video he uploaded contained even a censored version a sex scene in Hellraiser then that should have been a red flag for him.

I upload rarely enough that the upload wizard looks different pretty much every time I use it but the not-for-kids and age-restriction options are pretty prominent and both have links to gotcha pages that list how they should be used.