In Order of the Phoenix, Harry speculates that Dolores Umbridge might be a Death Eater, but Sirius replies that "the world isn't split into good people and Death Eaters". I think this moral complexity is the most interesting aspect the Harry Potter series.
To that point, Umbridge does appear to employ a sliding-scale of ethics as the moral landscape of the series shifts. This gives her a fairly unique perspective on the simplified "racism is bad" theme that the series seems to have been reduced to post Book 7.
My questions is: We know from Order of the Phoenix that Umbridge had an odd aversion to so called "half-breeds" (e.g. Hagrid, centaurs, etc.), but do we ever get any indication that she is prejudiced towards muggle-borns or half-bloods (or even muggles in general) prior to the fall of the Ministry of Magic or her obtaining the locket horcrux in Deathly Hallows?
Could this be a prejudice that developed under convenient circumstances or one exacerbated by the locket horcrux? Does she ever show prejudice towards muggles in general?