Dude i totally agree with your last sentence.
For my defence, i consider my self really open minded music wise.
I listen from Slipknot to Testament, from Death to Gamma Ray.
I even like bands like Massive Attack, Prodigy, Pearl Jam, Nirvana.....
I listen to whatever is rocking my balls.I don't care what magazines and TV and radio are advertising.
BUT... there is core like Heaven Shall Burn, and there is core like the guys in the OPs video.I think there is a big difference between the two.
As for the 15 year olds, not every one is like you or me when we were 15.
Proof is that 70% give or take of twilight fans are under age and the rest are fat,ugly chicks, nobody shags and that constantly masturbate to Robert Pattinsons poster.
Almost same thing goes with some awe-full core bands with bad music.Its the current trent and thats the way it goes.
Same thing happened a couple of years back with emo-kids.
Hell... same thing happened when Slipknot started to become famous, and only after they changed (a bit) their style and music, they gained everybody's respect.
Of course , there are always exceptions to this ''rule''