You cannot use an argument of whataboutism in politics (well, you can, but it doesn't have any effect). It isn't applicable in any way. It just establishes that one bad deed doesn't excuse another.

But in a political context when the topic is mutual standards of behavior, it can be justified because that overrides the determination if an action is ethical or not.

On the contrary it can be abused as a rhetorical trick to only let objections be permitted if the sender is flawless if the accuser takes the lead in pointing out mistakes.