This is pretty much there was even an entire debate as to whether corruption even made sense in CoC2 a while back and whether the demons are even evil at all.
Most of the uncorrupted mobs in the game rape you on loss by default, some even violating Cait's own sacred backdoor virginity to do so. Some even just outright rape others like you've pointed out. A significant chunk of the mobs, in fact,
aren't corrupted and are actually responsible for most of the atrocities that happen in the world. The kitsune are even worse in some respects since they unironically intend to colonise the lands you live in and view non-kitsune as simply free nourishment, barely even people.
Compare that to the demons. Sure, they also rape on loss but that's not an indicator of 'evil' nor 'corruption' as it were since it's established that the world is so sex-crazed that the act of raping someone is nothing but a mere setback. Hell, Kassyra, the supposed BBEG of the entire ordeal, doesn't even force herself upon you with her gigantic horse cock. If the PC at any point rebuffs her advances, she actually backs off which is more than can be said about the average non-demon.
Here's the worst the demons have actually done:
-Invade the lands
-Make some plants really horny
-Bimboify some bees
-Convince a sovereign ruler to give up her throne for more dickings and demonification
-Turn an entire village of centaurs exceptionally horny
I don't know about you but this sounds awfully tame for what is being touted as a multiversal threat.
Now, some might be thinking, "Surely, corruption must mean something at least", right? It causes physical transformations in people and makes that bean counter on your menu go up in points. Since we've already discounted sexual aggression as a defining factor of corruption be lieu of the world already being sexually depraved, what
does it do?
It makes you be more of an asshole--which doesn't matter since your companions love you anyway--and allows you to make decisions that are more
evil. Like kicking some bees into bimbo juice, and have a wonderful relationship with the grand demon herself.
So, not only does corruption not make any sense, it doesn't even have much meaning and the demons really aren't that bad when you consider what the non-corrupted world already does to you.