...sects (not sex).
It's a recurring motif in wuxia (Jin Yong used it directly and explicitly in both HSDS and SPW, and perhaps more peripherally in several other works) that more than one author has explored (Gu Long, or at least his ghostwriter, also made use of this motif in FULL MOON, CURVES SABRE): a supposedly "demonic" sect, shunned by mainstream wulin and condemned as being murderous, cruel, and unorthodox, demonstrates itself to in fact be composed of brave, honorable, and noble heroes whereas the supposedly heroic, respectable, and orthodox mainstream sects are in fact vile hypocrites.
Why did this theme fascinate wuxia writers so much, and what were the writers actually trying to tell readers? Considering that wuxia writers are predominantly Chinese (or otherwise East Asian), a culture inclined towards conservatism and suspicious of and resistant towards changes that challenge tradition/the status quo, were the wuxia writers advocates of ideas that were, by Chinese standards, radically subversive?