You got it.
It is a very clear ("textbook") example of psychological reactance (to perceived threat, loss of autonomy, choice or freedom, etc).
It is a fascinating, naturally-occurring, psychological mechanism aimed at attempting to restore freedom. It is easily observed in children, but some carry it into adulthood. It gets really interesting when the perceived threat comes from what is perceived to be an in-group source as opposed to out-group source. And if you go through the entire thread you will see a real life example of the mechanism in action. Absolutely fascinating!
(P.S. Whataboutism is just one method of reactance with specific characteristics, which you have mentioned earlier).