What has this parent done that makes them ineligible to criticize others?
It's a method of deflection.
"Whataboutism' is a rhetorical device that involves accusing others of offenses as a way of deflecting attention from one's own deeds."
Variations of:
"Hey can I get back that $50 I lent you? I always pay you back and thought we had a mutual understanding, what gives?"
"Nice whataboutism, quit trying to make it about me."
Also your example isn't even whataboutism which is defined as "the technique or practice of responding to an accusation or difficult question by making a counteraccusation or raising a different issue."
What other accusation or difficult question is being raised in your example? It's person A asking for money he lent to person B back and pointing out what when person B lent him money he paid it back.
That's why claims of hypocrisy against the other party, backed up with examples of the same behavior in other situations from them instead of you, can be cheaply dismissed as "whataboutism".
However... visa V mastercard , using whataboutism is valid in this situation. Bringing up something the US government did in the past to silence the criticism of a US citizen to another countries actions is wrong.
EDIT: Just another thought about your example. There isn't even hypocrisy. Person B lent money to A and A paid it back, then Person A lent money to B and B didn't pay it back.
- B doesn't pay back money
- A pays back money
There's no contradictions in their actions.