doing so is, in effect, a form of theft,
In a matter of fact that isn't true. If someone is rewarded for sharing ideas it is not akin to theft, it is just a reward for sharing those ideas. Now if we could take the idea (in this case the video) away from computingforever's channel on Youtube in a way he wouldn't have it anymore. That would be theft.
I strongly disagree with the claim that when someone's potential revenues MAY get reduced (which more likely isn't the case) for copying or sharing his work, that consitutes a theft. It would mean that whenever someone simply downvotes your comments on steem and your potential revenue gets smaller that's a theft too. And that just isn't the case.
Thank you for sharing, gamer00. My comments are based upon the comments YouTube creators, and also on patents. The two primary complaints I've seen are actual theft of the creation (eg: a high-speed video was edited to show just the part a company wanted to use, with no attribution or royalties to the creator), and loss of revenues because of being displayed on other platforms that don't return revenues to the creator - in that case, Facebook. The creators were LOSING revenues, which were being taken via direct theft of the creation or via non-compensated viewing on other sites, and their complaints were (at the time of making the complaint videos) ignored. When a creator loses revenues, and those revenues go to another party, that is theft.
Put it another way: You make an original painting. Someone duplicates it and sells it as an original, which is clearly illegal according to existing laws on artwork. They do not recompense you, although they do sell it as your product. You have lost the revenues from YOUR work, while that person pockets the money, minus expenses. That is the same basic thing as posting other people's videos and getting money "for sharing them", but it is worse because, whereas selling that forged painting is a one-time sale, this is repeat business (on steemit, until the payout period is finished).
I do not agree with your final sentence and it is a different issue.
Thanks for taking the time to give your input. Only by communicating our thoughts can we improve steemit.