What a loser Japanese MC with no mind. Not all normal Japanese MC's are subservient men who are willing to immediately serve anyone in power without learning anything about him like a fucking dumbass, not when he's on the losing end.
If they were fine with enslaving non-humans, giving them MORE power is only going to make it worse, and like normal humans, you can't change their opinions on non-humans be inferior species overnight, so what he is doing is basically giving humans more power, with getting nothing in return, when he can just power through negotiations.
This isn't a civil society where every race is just the human race and you can do it through "mutual understanding" or non-violent protest. This literally only works because in our world, every race was a human. There are literally many different anthropomorphic species. Its entirely different from just skin color. They literally consider them non-humans, so they can kill them non-chalantly like the Japanese Army killing the locals in WWII or Nazis in the holocaust. They are the evil, what the MC is doing is essentially saying to the Nazis, well, shit, heres your nuclear bomb (which by giving them advance technology = more humans = more power = killing all other non-human species, especially since the gods don't give a crap about species other than humans from the way the goddess phrases it).
Especially in medieval times, you can't change the society from the top, you HAVE TO do it from the bottom. This means, revolution, or in this case, massive amounts of violence.
MC is a fucking dumbass with no brain cells. If this doesn't come to bite him in the ass, then I'm dropping this series. I can stand dumb MC's making dumb decisions if it leads to tragedy later as a means of character development, but if this all turns out well, then its just a shitty story with a dumb MC where the world works for him, in the stupidest most plot convenient way.
tl;dr God, I can't believe there exists a series that can make loathe the MC in just 1 line. This development is just so cliche and dumb and never more have I ever hated the phrase "So be it".