Consider the phrase "be real with me" colloquially means "be honest with me". Also "real talk", "your real self", etc.

How can mirrors be honest if our eyes aren't honest?

Kid wasn't wrong, in fact, was quite right. People are in denial about their outward appearances never mind other things) all the time. People with anorexia see themselves as overweight when they may actually be dangerously underweight. People think they're ugly when they're not. (Conversely, may think they're really hot about when they're not.)