Nietzsche would reject any kind of popular movement having once written that popular opinion is always wrong. Always. He would also reject any and all overtures of popularity in Prog as he rejected the popularity of German unification. At one point in time, Nietzsche lauded the music of Wagner for its sophistication and elevating qualities, but then came to despise Wagner himself - for accommodating popular opinion. And let's face it - this is a commercial form of music, just one that sells in relatively low numbers. I doubt that any one of our beloved artists would bewail any significant gain in popularity. Remember that many of the classic artists went populist. I do not think he would really care that much about an individual's opinion but he would challenge whether that person was being truly individual or not. And this is the too-often missed aspect of his philosophy. Mastery is not master over others, it is mastery of oneself.
As to the second issue, Prog is not overtly sexual, but themes of love and romance exist. There are those of us who are neither attracted nor titillated by the booty shaking nature of current pop music and find Prog and other genres far more stimulating in that manner (as well as intellectually). I find the music of Vangelis far more sexy than that of Beyoncé. So, no, Prog is not nonsexual, but it approaches the subject in a sophisticated and intelligent manner, nor is that its only subject.