Are Cannibal Corpse a serious band?

I always digged the sound, but I just started reading the lyrics for the tracks on an older record, Tomb of the Mutilated. And it is...very disturbing. It's almost as if they are just writing them to be stupid and humorous. And yes, I know this is death metal. But some of this stuff makes you sick just from listening to it. I mean, it's really over the top. So I'm curious - are they a serious band? Or do they do this stuff kind of as a joke? I know they have a killer live performance and everything, but the lyrics suggest otherwise...