@redpandamaniacal
I am referring to:
a person or a group covertly sows seeds of doubt in a targeted individual or group, making them question their own memory, perception, or judgment
Our MC is doing neither. He's just uncovering contradictions in their stated reasons for their behaviour. Clearly the kids will not go and say "we're bullying her because we don't like her/we're bored/we want to play out some authoritative figure" and will rationalize their behaviour with bs. He's just not letting them use this bs, and since people are in general unwilling to admit that they are acting like villains it causes cognitive dissonance, and they give up and run away. Note that what he's doing is way beyond the capabilities and understanding of a kid, and while the manga tries to pass it off as a result of his "innocence" it's implausible. But it's a manga, so who cares.
Yeah, the bullies are trying to emulate a "parent" state, but the MC basically doesn't let them by not acting like a child or a parent would (by giving into pressure/ getting pissed) but rather as an adult. This flips up the dynamic to where they perceive the MC as the one in the parent state (adult and parent state are hard to differentiate for kids, especially if they are younger) and themselves in the child state, which causes them to feel "defeated" and give up. To be sure, the implausible part in the whole thing is the MC's convenient honest misunderstanding of the bullies. I can buy that he does this intentionally but pretends not to, I cannot buy the "innocence" argument - there's only so long this can work irl. Fortunately this is not irl.