I'm, for the post part, against it.
However, I'm only against what YouTube is promoting - unexperienced fighting, and often longfinned bettas. If the bettas aren't fatally wounded and can be cared for after, I don't see harm in it.. but I doubt that is happening with those videos. However, I don't agree with the no offense policy being incorporated - something is going to be offensive to some people while others love it, and though I do think it's encouraging unexperienced teenagers to do it, there really isn't anything we can sufficiently do.
I am totally against allowing 2 bettas to fight. You seem to think death or injury is the only bad side to it and since they live, it is a good thing. What about the stress involved to the fish? The losing fish has to be fearful for his life. Fighting any animal is not an art form, it can never be regarded as harmless or amusing.
If you want to see agression, if that's what presses your buttons, go to a boxing match and watch 2 humans thump the living bejaysus out of each other. At least they have a choice about it and the loser could run out of the ring or submit and the beating would stop. Where is the terriefied losing betta to go ? Where is the timid betta who doesn't
want to be in the same tank as another betta go?