
The old man made the medicine thinking it'd help people without thinking of side-effects and he believes that he stands above everyone and so, he blames all the people who use the medicine and succumb to it rather than acknowledging it's his fault. Or he's just plain evil and believes poor people don't deserve to live.
He's not about to bone a horse is he...
I think he did so once before, that one chapter where he woke up naked in the lake? was that no the horse xD ?
Don't even remember, this manga is just a fever dream