I suppose it would really depend on how the queerrats are indebting the children to them, but the bigger difference is that I doubt they are true Fiends.

They feed them, care for them, maybe even treat them as something special, so the "fiend" sees the queerrats as their family/allies. The "other" that the queerrat-raised-fiend would hate and loathe would be the regular humans. It wasn't hard to see how Maria and Mamoru's child viewed the queerrats as friendlies (6:50). I would be surprised if any queerrats had died by the hand of this fiend. The "otherness" of humans is reinforced every time the Queerrat Fiend witnesses members of their "family" callously murdered by humans with Cantus.

So the Queerrat Fiends aren't Fiends in the traditional sense. The regular Fiends suffer a mental break, out of rage or isolation or whatever. Pure psychosis. The Queerrat Fiends simply aren't trained and have zero discipline or restrictions on their abilities. They are simply raw power. A return to the original murdering Espers from now-ancient Japan. The queerrats don't control them, but they do not have to fear them. They're family.