Ofcourse their last CD contains a track called "And that's how I became a Satanist"...
But either way, I always saw Entombed lyrics as much more tongue in cheek than a lot of other bands (same goes for the song I just mentioned). I really don't think they have any kind of serious agenda at all. They're a good band though, and I'm not one of those purists who thinks they "sold out" after Clandestine. Almost all of their subsequent albums are great and well worth listening to if you like your death metal with a hint of rock & roll groove (death 'n roll as they call it themselves) and maybe a few punk elements here and there. Recommended albums: Clandestine, Wolverine Blues and Morning Star.
Fun band.