I think it's not like that, I mean, Nightmare Moon wouldn't require such frivolous thing to her subjects....actualy their behavior kind of makes sense to me...- Rarity being unpleased with Spike's presence:As we could see on episode "Dragon quest", and "Secret of my excess" dragons are known for their greed, evil actions and gem eating behavior. They would smash a nest of phoenix just for fun. Of corse Spike is a exception to the greed and evil actions stuff, but on "Nightmare Moon" timeline, Rarity never met him (probably he doesn't even exist on this timeline).For a classy and jewery loving mare she is, of course she will despise dragons. They can be considered a threat to anypony for their violence and stuff.- The guards agressive behavior:I think they might be obeying not just because of fear, but mostly because she is the only authority they can rely on. When they shrink when hear the name of Celestia, that might be because they kind of miss the sunlight; feeling awkward about the ex-ruller stuff or they are kind of traumatized about the violent fight that they witnessed...being cold to strangers might be caused by the fact that you don't know what hides in the dark stuff....of something like they don't thrust anypony whith a strong magic (kind of like the equestrian ponies about the villains)at least it's my opinion about it...