That phrase is used for everything from verbal interrogation up through torture. And when you are trying to root out channeling enemies, sometimes you have to go a little further. That kind of foe cannot be left to do the unimaginable harm a malicious channeler could get up to.

I think a large problem most of the readers have with the Children and the Seanchan is that none of them can escape the PoV trap and see things from the perspective of channeling being bad. Three of the five main characters can channel, so we are predisposed to believe the best of them and give them the benefit of the doubt, but the few of them as too dangerous and a menace has valid basis, especially in light of their history. What is more, I think most readers have not given serious thought to the problem of having to fight channelers without that ability on their side. "Extreme" measures that violate standards invented in a world with no supernatural manifestations cannot be dismissed out of hand.