Kids behave badly sometimes. It's just part of being a kid. They're constantly testing boundaries to figure out the rules and to learn how much they can get away with.
Unfortunately, this can often cause some frustration for the adults who are tasked with taking care of them. There's still this idea that caretakers should never express when their kiddos are being jerks.
I mean, obviously we're not going to call them jerks to their faces! But it's totally normal to think it, feel it, or even say it under your breath.