I haven't read the whole thread so this may have been mentioned.
Why not flag any video of betta fighting you see as containing inappropriate content, Then at least just casual viewers of you tube will have to go through registering just to see it. And add a comment to the video page. But as far as getting it taken off the site, everyone's free to post whatever video's they wish to so that would not happen.
That said i think for any animal to be put into a situation where it has to fight to the death is deplorable and should be banned. It is illegal to hold dog fights in many western country's and cock fighting too, but because the betta is a fish, it appears that it doesn't really matter.
That said, dog fighting and cock fighting happen illegally anyway, so making it illegal wouldn't stop it anyway. What about kids sticking two bettas in the same cup at the LFS. That's just as bad, but LFS's still keep putting the fish in cups that the public can get to!!!