I think 'to say they have no security concerns re Ukraine is sophomoric at best and blatantly dishonest at worst. No, of course Russia isn’t worried about Ukraine invading but a child knows they worry about the US and NATO' in reply to the person saying it, will be interpreted by 99% of people as insult.
I don't view U.S. government as precious. I look at your scenario the same way; in practical terms, is this a valid concern? We have long, stable relations with Mexico, buy 80%/$330B of their exports while China buys <2%/$10B. Mexico isn't wrecking that.
Russia is not a good neighbor of Ukraine. Ukraine doesn't have nukes, Russia does. NATO, nor anyone else is going to use Ukraine as thoroughfare for Russian attack unless Russia attacks NATO. NATO isn't going to attack nuclear Russia. That's it. That isn't going to happen and to think Putin doesn't understand that practical reality is the simple-minded rubric you allude to. His security claims are that rubric. Even if Ukraine were in NATO, no one is attacking Russia unless they move on NATO.
I think likely he'd have taken Ukraine after Crimea if Biden had succeeded him. He's made clear that Ukraine is going to stay a relatively poor, 2nd world country in Russia's orbit because he intends to directly have it or indirectly control with a pro-Russia regime. His statements Ukraine has to be deNazified and demilitarized are just another rubric layer. He's gaming the West just like M. East experts were gamed by a scraggly bunch of Palestine Arabs for decades, and convinced the world no peace without kowtowing to them.
People who feign to be suspicious of everyone around them are those hiding themselves as being the worst offender. That was the point of my comment re: Putin's SC endorsement then, that he violates now, not that it has served as restraint.