Yeah, I know about this line of reasoning, and it has some ground. Russia 'shouldn't ' tolerate that and it made steps to thwart that. How successful they were, the time will show.
But I like this way of reasoning 'It is not NATO expanding to the East, it is the East joining NATO'. A dozen countries from Estonia in the north to Bulgaria on the south joined the bloc voluntarily. That was their conscious and sovereign choice. Somehow, the history shows that once a nation was in Russian sphere, it doesn't want anymore to get back into that. Strange, eh.
There was the time when the US had to cope with a pro-Soviet hostile regime in Cuba with military bases there. The Putin regime should learn how to cope with a 'hostile regime' in Ukraine. (It may not happen this way, of course. It is just my wishful thinking).