Yes, it'd be sadistic to teach the class "25 ways to mis-tie the running bowline". But I don't see how disaster videos like the two examples above can set up a bad thought process. They certainly don't have an ill effect on me. In tree work I think it is healthy to be ever-mindful of all the ways a thing can go wrong.
You need only look at some of the videos posted here and the ensuing comments to see that different views of right and wrong arise about the same video.
A video has to be pretty stark and the viewers have to be able to see the mistakes if you are to use the video effectively.
A really great example is the new employee that has bad technique and no approach to safety because of his previous experience. Show him a video of the same techniques and he will think it fine, the video will reinforce his beliefs.