The post title really spells out why I hate these people. They think that their disregard for verisimilitude is perfectly acceptable, but get pissy when somebody tells them to suspend their disbelief just the slightest bit. After all, how dare people want Medieval European Fantasy to look like Medieval Europe, and how dare they think that having a cast mostly composed of beautiful people is an acceptable break from reality!
I know I should probably oppose the Power Girl statement on principle due to my hatred of the "verisimilitude no real cuz magic" line, but I still comprehend the point clearly: superheroes, as a sort of American God Mythos, represent human glory and components of existence personified into an idealized human form, and so Power Girl being a buxom bombshell is par for the course of those design principles just as Superman is designed as a tall, muscular, and ruggedly handsome man. Complaining that an idealized woman has physical traits that are considered exceptionally desirable is stupid if you're not also going to complain about her being a literal superhuman with abilities far beyond what is normal for humanity.