The Democratic People's Republic of Tankiejerk

Calling out hypocrisy can be valid but it must further discussion, not shut it down. In your example, if country A is committing genocide while condemning country B for genocide, the problem isn't just country B’s actions. It's that country A is deflecting from its own crimes instead of addressing them.

Saying 'what about your genocide' only matters if it leads to accountability for both. If it's just used to avoid taking responsibility, then it's whataboutism. It shifts the focus without solving anything.

To reiterate, whataboutism is deflection meant to shut down further discussion.

Appealing to hypocrisy is a fallacy, full stop. Someone can be a hypocrite but that has no bearing on whether an action is justifiable for both/neither.