Hater Youtube Videos

I'm horribly confused. On YouTube many people post videos (obviously) but som people especially an account which I won't name has posted numerous videos dissing bands such as All Time Low, The Academy Is, Panic! At The Disco, Paramore (and all FBR bands for that matter), Tokio Hotel and Metro Station. They also say you shouldn't be a fan of such bands.
Now, why would you waste your time making videos that most likely will not change the viewers musical taste which is the whole point of the video. And also if you hate said band so much why dwell on them? Move on and make videos about bands you like. And when you are horrifically cruel to said band and people post nasty comments under the video is it really justifiable to be upset.
Maybe I'm wrong, or right or in between. Leave your opinion if you want.