A lot of the power metal fans I've seen have been shit... mainly because the majority of ones I've seen consider anything more extreme than power and melo-death to be shit.
The same as the worst type of people anywhere else: the arrogant narcissists who turn down their noses at anyone with different opinions (and not in the facetious mocking manner that lots of people online like to do). That's not unique to any one subgenre.