There is a distinction between an explanation and a justification. There are many ways to explain why some thing happened or might happen. They can not be used to justify said action. I believe Mearsheimer and Pozner, for reasons, confound one for the other. Saying that Russia could not help not to attack, that it is the rational choice for Russia, is like saying that advertisers can not help themselves tracking users, it is the rational choice to track users. Again, explanation is not justification. Explanations are not excuses. That is why I call it bullshit propaganda: He is justifying the war.
War is not just. War is never just. War is death and tragedy, even if you can write entire books explaining how it happened and why every party had legitimate interest.
RealPolitik, the realist school of thought, evolutionary psychology, etc. only ever provide explanations. And often they may be good explanations. They are useful when trying to understand events or people or groups of people and when trying to predict behavior or create models.
But to derive justification from those explanations means that you ascribe to the belief that determinism (lack of free will) absolves you of responsibility. It does not. Whether you have free will or not you still have to make choices and still bear the responsibility of those choices. If you believe you have free will you are directly responsible and must assume responsibility for any consequence coming your way. If you believe you do not have free will, than any consequence is simply the system correcting itself. There is no escape from making choices.
But what do I known? So since you are claiming he has more authority I will counter with someone of equal or greater authority, Alexander Stubb, past Prime Minister, Minister Of Finance and Minister of Foreign Affairs of Finland and Director and Professor of the School of Transnational Governance at the European University Institute:
https://www.youtube.com/watch?v=vlB-pRqdyBg