Firstly, who said ultra-competitive cannot be fluffy? The two are not mutually exclusive. Many of the most competitive Imperial Guard lists would fit even the most dogmatic view of the fluff.I'm saying, playing ultra-competitively and trying to claim you aren't because of some bizarre distortion of the setting is disingenuous.
But they would be completely right to tell you that's it's in line with the setting. Just because it's not a letter-perfect recreation of the Space Marine army from Fall of Damnos or Orar's Sepulchre doesn't mean it's not a fluffy Utramarine army.I don't have a particular build in mind which violates what I would consider good conduct so I don't really have any emotional reaction or aversion to the named builds you listed. Nor am I referring to 6th edition specifically. I think this same position can be expressed in almost any similar game. And I can think of a few armies I faced in previous editions which were abusive. Though I don't think any of my opponents ever had the gall to try and tell me that they were fielding an army right in-line with the setting.
Which is fine, and your choice (I'm not sure if I would avoid somebody because they hold different values, because if I did I'd rapidly be alone, but I think I see your point), but this is a list-building tactica i.e. a way of making your list better. And as you said, some choices are objectively better than others. What this tactica isn't is a discussion on whether competitive armies are fluffy and fulfill one's desire for a cinematic game, because everybody has a different opinion on what follows the narrative as this past page has so aptly demonstrated.Mind you this isn't a witch hunt. When "I see it" I just generally avoid playing those people because we clearly value different things. I don't go about brow beating them over their narrow minded fluff-apostasy.