If someone claims they’re driven by a moral principle, then you check they’re consistent about the principle.
That’s not whataboutism. The meaning has changed over time.
Example:
Tommy says:“You can’t support the Provos because they committed war crimes.”
His syllogism is:
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Major premise: No group who commits war crimes can be supported [this is implied/hidden]
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Minor premise: The Provos committed war crimes
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Conclusion: therefore the PIRA cannot be supported
Now if I say, “Do you support the Thatcher government? They committed lots of war crimes?”, I am asking is he sincere about his major premise.
If he’s not sincere about his major premise/moral principle, then he is insincere about it, he is hypocritically moralising to score rhetorical points.
If he is true to his principle, he will apply it across the board.
So whataboutism is good and reasonable.
I don’t think your example really fits the definition of whataboutism. That’s just calling out hypocrisy
“I’m too full to finish my meal”
“But there are kids starving in Africa!”
That’s whataboutism. Bringing up a counterpoint that sounds relevant but actually isn’t.
My example is the original meaning: https://en.wikipedia.org/wiki/Whataboutism#Origins
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