> A lot of current news feels very biased, even from sources I previously found unbiased.
I wholeheartedly agree. I feel like I could write an entire book of what it reveals about the state of Western culture. But when something is so obnoxious I try to remind myself to be especially careful about how I react. Because one of the other obnoxious things about contemporary Western culture is how partisan political sentiments are driven by spiteful contrarianism.
> he very clearly explains what has led to the current situation.
He very clearly explains his opinion, at least. Much of what he says is pretty much consensus opinion. The U.S. and Europe did push NATO expansion too aggressively. (Though that's different from saying that it was wrong to include, e.g., Latvia and Estonia, which IIRC is a claim Mearsheimer wasn't willing to state outright.) In fact, this was a moderately important point of domestic U.S. political debate which even featured in the 2008 presidential campaigns; particularly regarding ABMs in Poland.
One of the flaws in his PoV is that none of it actually justifies Russia's behavior. It makes most sense only if you conceive of Russia as a scared child, rather than a hyper rational, deliberate, realpolitik actor, which most people (until recently) consider to be Putin's M.O. It also ignores the fact that Germany, France, and even the U.K. were more restrained than the U.S., and Russia well understood that there were some bright lines those countries wouldn't cross (and the U.S. couldn't force them to cross), especially after the dust settled from the 2004 expansion that put NATO on Russia's doorstep.
Moreover, we're 6+ years on from that speech and the status quo had only further solidified. That's why Russia in 2014 and now in 2022 knew with absolute certainty that NATO would not directly intervene in its invasions of Ukraine. At most there'd be a proxy war, but that's typical Cold War realpolitik and Russia couldn't with a straight face call foul.
No observer can seriously dispute that Europe and the US had as a practical matter committed to and contented themselves with keeping Ukraine and Belarus as buffer states, at least in terms of military posture. Now, however, everything has been upended. Russia's revealed, hard irredentist ambitions has fundamentally changed the situation. If Ukraine ends up in the EU or even NATO, it'll be a self-fulfilling prophecy, not because things were inexorably moving in that direction.
This is all a long-winded way of saying that just because Russia had very legitimate security grievances does not, by itself, explain or excuse the Ukraine invasion. To my ears (having studied International Politics in college and staying apprised of events over the past 25 years), Mearsheimer's speech borders on a dangerous apology of Russia and other authoritarian regimes. His factual recounting is on its face reasonable, but those facts only beg the question. The question is whether Russia was justified, according to even the most conservative, zero sum, realpolitik perspective, in invading Ukraine in 2022. The answer is a resounding, "No". Just as the answer to whether the U.S. was justified in invading and overthrowing Iraq is, "No". And in neither case were those decisions inevitable, nor does culpability lie anywhere other than with the invaders. The U.S. for its part recognized the inexcusable harm the Iraq invasion did to global and American security stability when Obama took a huge bite of humble pie (both personally and on behalf of the country) and refused to escalate in Syria. Unfortunately Putin, like Bush in 2003, has already committed Russia to carrying through an unforgivable injury to global and its own security stability.