If you say something and newbies realize you know more then they, perhaps they could listen. If not, the worst thing that could happen to you is you could have the assurance that you did all that you could. If not, you might be regretting you never gave your opinion. And, who cares what the newbies says anyway. No one can think of everything, accidents happen, I would never tell you to mind your own business Oenophore, unless you starting pulling on my rigging while I was leading.
Most of the time I have had favorable results when correcting newbies, they usually are very interested.
As for those two videos, I think for the first one you would *really* have to know what is going on, but obviously the person should have started down climbing rather then going for it in questionable circumstances.
As for the second one, you could tell them to stop and do almost anything else at any point, and you would be giving them correct advice.
I think you are exaggerating.
The Mohonk Mountain House and the Mohonk Preserve have done a great job protecting the environment thus far, but ... it's all down hill from here http://youtu.be/9AU8fMo8v4k.