As Chainsaw Ash said, there are two types of grain:
-dupe grain
-emulsion grain on the camera original
Dupe grain is bad. Its a foreign element that comes from replication, and resembles a mask of dirt over the image. Nearly all of the grain on the GOUT is dupe grain. Its basically like a photocopy of a photocopy--each time you replicate it, the image degrades, in the case of film you get extra grain added. This should be removed, or more importantly bypassed by going to an earlier print thats not so far generationally removed. Grain reduction software often just fuzzes it out by blurring the grain, which just degrades the image further.
However, film IS grain. This is emulsion grain thats on the camera negative. Its like saying "lets remove pixels from digital images." Its a nonsensical statement. Digital images are composed of pixels, and film is composed of tiny crystals that form an image, and are called grain. There are different types of grain, which vary by size and other factors. But this literally IS the film---the detail is made up of grain. Sometimes the grain is slightly bigger, sometimes its finer, and the grain size is deliberately chosen by the cinematographer--but its always there. This should not be removed.
However, people have this image of old movies being all grainy and shitty looking. They're not. Thats the dupe grain, because most old movies are made from old, generational prints. The 2004 SE is actually a very accurate reproduction of the camera negative. If you look at it you can see grain in the image, because the image is grain, but there shouldn't be a mask of dirtyness over it like in the GOUT, that is all foreign. I think the SE might have had a bit of sharpening done to it, but its basically a close approximation of the camera original. But this doesn't apply to all films--some films have much more noticeable grain structure, and some films actually use a visibly distracting heavy grain for purposeful effect.
Anyway, grain is good, its the image, its what the image is composed of, it has a texture, its like saying lets remove the brush stroke marking from oil paintings--well, sorry, thats what the image is composed of, its part of the aesthetic. However, I think the nastinest offenders are often dupe grain, and this is not part of the original image. Yet removing it just makes things worse, you just blur out the detail. Basically, you have to just get an original negative so that it doesn't have dupe grain, and if you can't well then you are shit out of luck. Such is the case with the GOUT. But people often still complain that Blu Ray brings out the grain in films--it sure does; thank god we can finally see films they way they actually look. Film has a texture; people just aren't accustomed to seeing it on their TVs because they've never actually seen this sort of STRUCTURAL TEXTURE, as opposed to dupe grain, before because home display has never been capable of displaying it.
As for the topic--you know, I've seen a million reasons of people trying to justify why the films are colored the way they are. The simple, painful answer is that its just shoddy workmanship and poor taste. I wish it were otherwise. Lucas wanted the films to be saturated, high contrast like the prequels, and with a more bolder color pallete, someone totally fucked up implementing this, Lucas was an idiot and said it looks good, everyone else was afraid to say it looks like shit and Vader has pink lightsaber, and voila, Lucasfilm just made half a billion dollars in video sales.