"Precedent" is actually pretty fundamental to tons of legal systems. Because yes, it is important to call out hypocrisy. The people most concerned about whataboutisms nowadays are usually just using it as a way to completely avoid self retrospection and shield themself from what they are accusing others of. Yes, sometimes it is a non sensical argument (when you bring up something completely unrelated), but it is a very very overused online buzzword now.