How does Atticus relate Mayella's "crime" to the lives of children? Why would he try to simplify her offense?

In Chapter 20, Atticus is giving his closing speech explaining Mayella's crime and says,

"She did something every child has done—she tried to put the evidence of her offense away from her. But in this case she was no child hiding stolen contraband: she struck out at her victim—of necessity she must put him away from her—he must be removed from her presence, from this world. She must destroy the evidence of her offense. What was the evidence of her offense? Tom Robinson, a human being." (Lee 272)

Atticus relates Mayella's crime of perjury to a child attempting to discard evidence because her motivation to get rid of Tom Robinson is similar to the way children are motivated to get rid of evidence when they are about to get caught. When a child does something wrong, like steal a toy, they get scared that they will be caught and end up throwing the toy away out of fear. The idea behind Mayella's choice to "get rid" of Tom Robinson is similar to a child's choice to throw away evidence. However, the major difference is that Tom Robinson is a human and one cannot simply "discard" a human being. I believe that Atticus chooses to simplify Mayella's crime so that the jury can understand her motivation for committing perjury. Most people can relate to discarding evidence as a child out of fear that they will be caught, and Mayella's decision to falsely accuse Tom Robinson is no different.