Ah, I think I see where we are differing. Followers of chaos do promote death and suffering as a part of their worship. In my opinion, the followers see death as the eventual goal to be achieved through the spread of disease, where to papa himself, death is often just am unavoidable side affect.
Also, you are using a very human centric vision of what life forms are valued. A twisted, deadly form of a microbe may be something you, and most humans, do not value, but on a purely scientific level, not much difference between us in the grand scheme of things. We are born, we consume, we kill, reproduce, then die. You value one type life more, because of your natural biases. You could argue that Nurgle values life even more than humans as he is constantly trying to create more diverse types of life. Just because they are microscopic, doesn't mean they have less value as living creatures on a cosmic level.