As in this post, I'm going to discuss an applied example of the idea of counter-rhetoric. This example is to examine the expression "I'm an idiot." It's common for people with low self-esteem to exaggerate their faults and mistakes, and this expression, which I say or think sometimes, is a great example.
An "idiot" is a stupid person. Making a mistake does not make one a stupid person. Calling yourself an idiot in response to having made a mistake is therefore not a rational response. It is a huge exaggeration driven by emotions. A better and somewhat playful response might be "I am fallible, and I have witnessed yet another proof." A more straightforward response might be simply "I am a person who made a mistake." Any variation on these is superior to the irrational exaggeration.
Exaggerating your faults is unjust. Justice consists in treating people how they ought to be treated. You yourself are a person, and so you come within the scope of justice. If you exaggerating your faults, and condemn yourself, that is an injustice. If you treat yourself unjustly, you can't reasonable expect to treat others justly. If you can't even be just to yourself, how can you expect to be just to others?
There's also a psychological component, where if you lack self-esteem, you'll try to cling to others to get it vicariously. This can also involve treating them unjustly in various ways (for instance, being very demanding of their time and attention, and getting angry when they don't pay what you deem to be a proper amount of attention to you).