Most of this, the story hasn't told you or dropped any hints about. Even in this chapter with the rabbitkin girl, despite her not considering her situation the hero's fault, she told the parents that the Knight Order wouldn't help her because they deemed the hero's mission more important. Couple that with the fiancee's story and the hero has stopped doing his mission so both the hero and the Knight Order are meandering about but can't go help this village?
So, far, the story hasn't told you that it's not about the Hero not being OP enough, but is about the hero's morality and abuse of position and power. Sure, the author could twist that around, but right now seems the story will be about the author compiling evidence against their son. The parents are obviously upset because, so far, from everything they're hearing their son is not acting how they raised him.
Perhaps the author will pull something out like maybe the hero is being mind manipulated or something, we'll see, but I'd rather it stay as the hero got away from home and lost his mind and forgot his upbringing. Which happens with children who leave their parents, get a little freedom and go wild for a long time before regret kicks in and they realized they messed up and likely ruined their relationships with mom and dad by way of rebellion when they became adults. So, I'd rather see how this manga inevitably tries to reconcile the relationship between son and parents if the son is actually doing these things or see if their relationship will forever be broken because the son lost his head.