If women can be captured and used as breeding stock by the monsters in the dungeon, then they shouldn't be allowed to become adventurers in the first place. Even one of the captured still means multiple, or even numerous, more monsters endangering everyone. It's either stupid, he has a misunderstanding, or...well, hentai logic would suggest it's intentional for some nefarious group in control to make more monsters.
Speaking of which, it seems to me that he isn't reincarnated from another world, but from the one the series is set in. Or else there's just a lot of overlap for some reason.