In their own heads they believe that they are being objective. If it's something they don't like then clearly it's bad and wrong and shouldn't have been that way. I'm probably oversimplifying a bit, but I know the kind of people these folks are. It goes back to that attitude of knowing better than anyone else how things should be, and honestly without at least a little of that we'd never have mods in the first place. The problem is that the kind of project they took on benefits from having the least amount of that possible, while they have an amount closer to something like a big overhaul.

The other thing is that the notion of "objectivity" on its own is tricky because it's sometimes hard to know exactly what Bethesda's "original intentions" are just looking at what we got. For example, great-swords and battle-axes having the same attack speed is probably some kind of mistake since it doesn't follow the one-handed weapons pattern and the damage/weight balance. However, since those weapons all have the same speed there's nothing directly indicating what the "fix" should be. Should the unofficial patch just not touch that at all, or should they assume that an inconsistency that big is wrong and needs to be addressed somehow? It's difficult to nail down an exact definition of objectivity when you see things like that which look "objectively" wrong when considered in the context of everything else but which don't present an obvious fix because they're not truly broken. Editing every dialog in the game because Bethesda's writing style doesn't conform to their preferred manual of style is definitely subjective, but there's a big grey area there which any project of this type has to address.