In spite of your unwillingness to give a summary of his viewpoint, I went ahead and watched 80 percent of the video. I think there is value in it, but as a lesson in how confirmation bias works to distort reality.
From the outset Mearsheimer has a moral message, that someone has to be blamed, and to find out who should be blamed, one side or in the other. This alone undermines his academic objectivity, especially coming from an advocate of the amoral realist school of international relations. For example, why would a scholar assume that there can't be degrees of fault, a shared negligence, by both parties? How is it that, for example, Obama is guilty of something because he said Russia doesn't produce anything, but Putin is not guilty of provocation when he (or state press) mocked a President for his lack of manhood?
And who says, him being a realist, that "fault" is in any sense applicable if, as he claims, the great powers have inevitable desires and wants and actions that transcend any individual actors' desires?
One has the sense that Mearsheimer is working against himself, on one hand making Putin the center of expressing rational and plain-spoken objections for "Russia", while on the other dissing the western theory that Putin is behind Russia and his/their immoral actions.
Mearsheimer and McGovern use the typical rhetorical tricks, as much to convince themselves as the listener. They cherry pick events to make a case, ignoring other events, such as Obama canceling the European ABM system to keep Russia happy. They point out the cancelation of the open skies treaty, not pointing out that Putin was not allowing overflights of major areas of suspicion. They point out that Putin in 2008 may have considered NATO a threat but failed to note that that his public justification was to primarily to protect Russian minorities. They don't mention Putin and his Russian cruise missiles, breaking the treaty, or the NATO concession (prior to Putin) to Russia to not base permanent NATO forces in new member states.
And while he is dismissing Putin as the root of this crisis, he fails to address how it is that all this happens on Putin's watch? Not Yeltsin, not Medvedev (2009 to Jan 2012), but under Putin.
Did your speakers forget that Obama and Medvedev had an era of cooperation? They signed and ratified a new START treaty, voted to support the most comprehensive set of sanctions against Iran, provided supply routes through Russia for American supply in Afghanistan, got Russia in the WTO, and established far more liberal visa regime. Or how about the re affirmation of the US, UK, and Russia memorandum persevering Ukraine's sovereignty? That doesn't sound like a country who is deeply offended and driven to extremes because of NATO being perspective for Georgia in 2008, or later?
There is ONE common denominator to these Russian actions, i.e. Putin. Putin, not Russia, is the core problem. Every other US President and Russian President has got along very well.
When you know all the facts, and make all the connections, their analysis doesn't explain who's at fault, or than Putin.