Lets reverse it. Say scotland declared independence next year. They then announced an alliance with russia. Then russia wanted to put a military base outside edinburgh.
You really think the british or american governments would allow that?
See, either way, it doesn't matter. From a humanistic perspective, Russia butchering Ukraine and Ukrainians for daring to dream of a future unshackled to a crumbling oligarchy is wrong, evil, and worth countering. But, even taking your point about it being no different to the US or the UK not allowing Russian military bases in Cuba or Scotland (for example), that presupposes that the world runs purely on geopolitics.
And here's the cold hard truth for Russia if it believes in that dictum - geopolitics is a game played by those who can afford it. Spheres of influence are maintained by those who can afford to maintain them and back themselves up with enough social, economic and military power to dissuade nations even attempting to break free.The US is such a nation. Russia is not.
If Russia's logic is 'The US and the UK have spheres of influence, why can't we, there's no morals in geopolitics', they can't whine when the US attempts to undermine their sphere of influence, nor when NATO advances right up to their border, nor when every single European country on their Western border with the exception of their pathetic puppet Belarus ends up implacably opposed to them. As is happening now. Their only persuasive power is military, and they can't afford even to modernize that properly. And yet they try to maintain their spheres of influence against powers far more appealing to their neighbors and satellites - culturally, economically, socially, politically.
It's ass-backwards even if they are believers in the dictum of there being no morals on the world stage. Even China learned to keep their mouths shut and their intentions hidden until they were wealthy enough to pursue them. One oligarchic Potemkin state with a flailing military trying desperately to enforce their will by bombing their neighbors, playing at being the USSR with 1/100th of the power, is just pathetic, and needs stopping for that alone.