I'd agree if there was no editing done, but do you adjust brightness/contrast/sharpening, etc. at all? To me that's still manipulation.
^This. Even going back to darkroom with film, "manipulation" is common. IMO, the key for a nature photographer is to do it subtly, not to make something that you wouldn't see in the natural world. For me, removing a twig here or there simply eliminates a distraction, but the beauty of the art is that everyone is free to express it in the way they see fit.