Why is mainstreamed metal flowed upon?

I mean really? It seem's like people love to bash mainsteam music these days. I mean, sure, a few mainsteam bands do sound like crap, but that doesn't mean all of them do. Metallica, Megadeth, and Slayer are excellent bands that still hold up very well today. Even some songs from Ashlee Simpson where pretty good and catchy. Yeah, I know I just switch genres there, but you still get the point.

There are some bands that I prefer their more mainstream sound then their old sound, which just goes to show you that anything can be good, no matter how popular it is. I always hate it when people hate a band just because its the cool thing to do. (Look at Justin Beiber, but I would have to agree that he sucks, but I gave his music a chance).

You can't have mainstream without the underground and vice visa. They both can suck and they both can rock. It just depends on the music itself. So next time your friend or people rants on a album, check it out before dissing it to.