We have to. Short of arguing on first-principles, agreeing on them, and then using those principles to evaluate everything done on both sides, this is one of the top mechanisms we have to bring a spotlight to the contradictory mess we have on our hands.

Personally, I blame lawyers and prosecutors. A law should be simple, easy to evaluate if it was broken, and always prosecuted. And when it comes to punishments, they should be explicit and without the possibility of being altered.

We've gotten too complacent with making all these arbitrary rules, then fiddling with their non-enforcement and severity by virtue of reduced sentences.

Actually in matters of law (which this definitely is), "whataboutism" is just judicial or executive precedent.

This is like crying about whataboutism when a judge cites judicial precedent to justify a sentence. Good luck with that, it might work as a "nuh-uh" in online discussions but in real life, precedent does actually matter.

Incorrect - that’s merely how you’ve interpreted it. Is not whataboutism, it’s first principles to expose standards supposed as impartial.