I consider it quite narrow-minded to bash a whole genre. It is true that there are a lot of nu-metal-angst-lyrics-clones popping up on mtv, but it's the same in other genres - if something is successful, there are always people around to copy it. If you constantly deny everything you feel is too successful or too popular (irrespective of your personal taste) you will end up being one of those troo-blackmetallers claiming colored artworks are too commercial, or whatever...
I would consider neither Slayer nor Rammstein Nu-Metal, by the way. Slayer may have been influenced by Nu-Metal, but hey, they're still Slayer! And Rammstein are just, well, something else entirely.