"The pot callin' the kettle black"

This term is used to describe a situation where someone talks about someone else when they really shouldn't. For example if I'm not doing well in school and I yell at my sister for failing an exam that is "The pot callin' the kettle black". Obviously the pot is just a black as the kettle so who is that pot to say anything. But in my example me yelling at my sister is justified because her failing an exam is not good at all regardless of what I do. I know I'm not perfect but she's still wrong and I should be allowed to point it out. Now in other situations where the person is teasing someone else or talking down to them negatively is where this term comes in handy. Because now that's verbal abuse. But people still use the saying "The pot callin' the kettle black" loosely and as a kid I never understood it. Maybe that's just me.