As a fan of the show and the "real band", that's completely untrue in regards to both.
There were a handful of episodes either Season 1 or 2 where they kept re-recording their new album over and over because it wasn't brutal enough, and developed space-age technology to record their album on the purest recording material possible.
Brendon Small cares enough about real metal/music to go on tour to play the songs that he writes for the show, as well as for the fact that Dethklok has three albums available to purchase, each with about 15-20 songs on them. There's usually a new song in every episode as well.
Yes, this is all about a "fake" band, and it's probably hyper defensive, but Brendon and company care as much as any other band does.
I'm clapping. Thanks for educating that guy.