Board Thread:Warhammer 40k General Discussion/@comment-92.97.77.182-20130321145115/@comment-24944355-20141004061415

The reason that destroying humanity in 40k would hurt chaos more than the destruction of any other species is simply numbers. Basicly there's more humans in the galaxy than all other species combined so eradicating humanity would be a huge kick in the goolies to chaos.

Destroying humanity wouldn't kill off chaos though, that was almost certainly a self serving lie told by the Cabal, but it would badly weaken chaos for a time until other xenos filled the vacuum.