The phrasing here leaves me unable to tell whether or not use of whataboutism, or whether the word whataboutism itself, is being criticized.
My understanding of what makes whataboutism an -ism is that it is used with the specific goal of distraction. There's no example of an "innocent" case of whataboutism, since it exists specifically to defend something. In addition, it's an "Offensive defense", if that makes sense: it defends by attacking. The attack involved is usuallly true, but is often neither-here-nor-there, and isn't in good faith but a cynical attempt to put the opponent on the defense instead. The classic example is "
And you are lynching negroes". Traditionally, it is known as
Tu quoque, or "you also". Of course the thing that is whatabouted doesn't necessarily need to be morally equivalent.
It doesn't actually promote treating people lightly: They aren't actually promoting lenience or whatever, and whatabouters who compare soviet crimes to american hate would never do the same thing in reverse, since they on one side and not the other.
TL;DR: It's the principle of shouting "Let he who is without sin cast the first stone!" only when you yourself are under threat, and being the most zealous slinger of stones the rest of the time.