This thing keeps popping up because you guys are missing an essential element of this theme.
That element is dehumanization.
Aka treating people like they're not people. Like they're things. Like they're not valuable to one's self personally. Of course they get thrown at the minions. They don't matter. They're not significant others. They're tools. Receptacles for lust at best. Breeding tools for minions at worst.
Basically, the protagonist in these sorts of works generally isn't supposed to be thinking of these girls as people to love and respect and have a relationship with. They're more like that porn-mag you're willing to share with friends in high-school, and hey, if they get a bit broken and dirty, it's no biggy. There's more out there to be gotten.
That's kind of an essential element when corruption is the priority. Because one isn't supposed to care about the sluts like that. They're not a harem. They're cattle, minions, whatever.
As for the exceptions... Suzukuri is more comedic in nature. Not sure about Demonion, but it might have the same gimmick. The TD game is more focused on the pervert that gets Isekaied to that world and his desires than anything else. But it's hard to say because it never got a good translation...
Lunasoft games on the other hand tend to get surprisingly dark if you really pay attention. Undoubtedly, you're not supposed to be playing a good person in this one. You're playing a nut that agrees to do a Dark Goddess' bidding, which includes raiding villages, killing people and breeding monsters. Whatever humor may or may not be in the game, it doesn't change the fact that he's sending off women to be bred by things that kill them in the process. (Pretty sure that one of the generic monster breeding scenes implies that the women died in the process. The one for an ogre or devil or something...)
