It has become equally popular to use whataboutism in defense of one’s own errors as to attack those who do. But the concept is not one-dimensional; it’s use can be motivated under some circumstances.
The moral implications of the crimes my country commits are not affected in any way by whatever crimes other countries are guilty of. Thus “what about the crimes of others” has no moral legitimacy. The other way around though, the question becomes more interesting.
Chomsky has taught us the basic principle of moral universalism, found in all religions and cultures. It’s so fundamental that it must have its roots deep in our genes. It simply says that we must apply to ourselves the same standards we apply to others. Those who don’t do so “plainly cannot be taken seriously when they speak of appropriateness of response; or of right and wrong, good and evil.”
So when our media and politicians excel in condemnations of other governments, the question “what about our own crimes” is not just legitimate, its compulsory for everybody who wants to have “a moral leg to stand on”. Clearly, a government who has ordered (and ignored) the killing of thousands cannot condemn some other government for murdering a dozen. It must first rectify its own misdeeds.
That’s not to say that atrocities can’t be discussed and even compared. Some murderous regimes are certainly worse than others. Mechanism that foster militarism is definitely important to discuss, regardless of whom it concerns. And there are naturally many other aspects of violence in the world that should be penetrated and analyzed.
But one thing is self-evidently impossible: I cannot morally condemn others for the same crime a committed myself.