When viewed from the perspective of the slave catcher, recapturing Sethe and her children is just another job. He even reminices about the different strategies that other escaped slaves have used to try to avoid capture as if it is just workplace banter. From the perspective of Schoolteacher it's a financial move, capture the woman who still has 10 good breeding years left and pick up her children as profits. But for Sethe it is the unthinkable. So she does what she thinks must be done in order to keep her children from experiencing the suffering and the horrors that she experienced.
Another example of this perspective is when Paul D. confronts Sethe about this after Stamp Paid shows him the newspaper clipping. Sethe dances around the topic for a while before finally confirming what she did. Paul's reaction is to say "you have two legs, not four," implying that what she did was subhuman, animalistic even. This is another matter of perspective, again, Sethe thought she was saving her children from a lifetime of suffering, but in Paul D's eyes she acted like an animal.
An earlier example of this, is when Sethe overhears Schoolteacher teaching his nephews about characteristics, and how he analyzes Sethe's "human characteristics" along side her "animal characteristics." To Sethe this is the ultimate offense and what drives her to send her children away and make a break for freedom, but for Schoolteacher it's just another lesson about another creature.