I Hate Copyright

I am really upset about this. I was planning on going to Youtube today to listen to some of my music that I really love and haven't listened to in awhile, and this is what I find:
(Sorry for the bad quality) Ridiculous! Out of fourteen songs, five of them are no longer available due to copyright. What is up with that crap? What, people aren't allowed to make videos anymore, showing how awesome the music or the show is? Or wait, are the artists just so insulted that someone would *gasp* use their song to make-in this case-an awesome AMV? If no, then what is so messed up with the people forcing the videos off Youtube? I really don't understand. It took me about ten minutes to find one of the songs off of my playlist that got deleted. Ten minutes! Usually, I wouldn't have that problem. But today, I realized that people who had put the same music up had either been forced to change the music to something else, or had to remove their audio. What are people supposed to do if they're just trying to look up a song and it's deleted the same way, or the "supposed" audio is in fact a different song? I find this completely ludicrous.

If someone can explain to me why people are being so grr about this, then please, go ahead, enlighten me, because I really want to know.