I read the letter and it sounded like the "Bush Doctrine" of preemptive aggression. The claim is that Russia is by nature aggressive (based on a very long-term historical trend that does not include its current regime) and so aggressive action against Russia is warranted, regardless of the current government or any existing treaties.

The aggressive aspect of NATO is also minimized, which I think is naive.

I was in Ukraine in 2016 and saw the US fighter jets flying formations on Russia's doorstep. Calling that "defensive" is absurd. We now know that since the 1990s there has been a US goal to aggressively expand NATO mainly to suppress Russia.

The problem with this strategy is that it does not care at all about Ukrainian lives. As someone with family in Ukraine, I do not want my country (the US) wreaking havoc in the region. Thousands of Ukrainians are dying every single day right now, all because the US doesn't want to respect Russia's security zone. Mearshimer calls this the US nostalgia over the "uni-polar moment" when the US was briefly the only superpower.

Too much of the modern notions of American exceptionalism rely upon biases from that brief moment in history, to everyone's peril.