By your logic of NATO being on Putin's doorstep giving him justification, you give free reign to the most anti-American activities of Iran. We did have, after all, hundreds of thousands of American soldiers on their doorstep in Afghanistan and, at just about the same time, hundreds of thousands of American soldiers on their doorstep in Iraq.
You're just carrying water for dictators with a flimsy excuse, the idea that Putin had some justification is the logic of his enablers. Ukraine voluntarily gave up all of its many nuclear weapons that were left there after the collapse of the SSSR, which led to the Budapest Memorandum of 1994, in which Russia was supposed to help guarantee Ukraine's security.
When has NATO ever attacked a non-aggressor nation? Putin's supposed rationale was delusional at best but more likely that of a mad wannabe empire builder.
