You see that a lot in the guitar community. Anything new or that doesn't fit a traditional, pre-existing mold is dismissed as inferior. Anything non-traditional and obviously skillful tends to draw hate from those same people.
I don't see what could be qualified as non traditional in their music. It was run of the mill speed/power metal that was pretty common since the early 90s, or even the 80s if you stretch the definition a bit. Even from a technical standpoint they were fucking good but nothing ground breaking.
I always felt that the hate against them came from the fact that they became mainstream popular thanks to guitar hero while they were not particularly notable among their peers in the metal scene.