"You are the parent, not your child's friend!" Herein lies another tragic loss wrought by the either/or mentality of conventional parenting advice.
Why not be a parent AND a friend? After all, a friend is anyone you know, like, and trust — all worthy qualities of a parent-child relationship.
Certainly, we want to be knowable and trustworthy to our children. Being likable is good, too, but it's often confused with niceness. When friends sacrifice authenticity in order to be "nice," healthy boundaries go out the window. That's the kind of "friendship" you don't want with your children — or anyone!
A true blue friend is one who puts trusting and knowing above liking, so s/he's willing to be totally authentic with you about his or her boundaries and limits. And don't you like knowing that your friend is who s/he appears to be?
Children who haven't learned our culture's sanctioned inauthenticity can teach us a lot about being a friend. They hide nothing (knowable) and always speak their truth (trustable).
Whether they can be so transparent and likable is up to you: Do you like realness more than superficial niceness?