We really don’t know why their mom was so mad. Kevin may have done something he wasn’t supposed to do, rather than not do something he should have done.
There’s really no reason to demand that the very flexible human mind not entertain two thoughts at once, even when they appear to be in conflict. In this case, wishing that there was a less painful way to solve an irritating problem is actually quite normal.
Ugh. We are all forked.