If you want to know why people don't take the BBC seriously and have a bit more respect for the Russian position, it is because 60% of those arguments are just not taking a serious situation seriously.
Armies don't just charge out because Putin has his "dream", and certainly not sustaining the sort of punishment that the Russians have had to undergo in Ukraine. We can see from the response to Prigozhin's coup that the military actually supports the war to a significant extent; if it was unpopular then Putin would have been rolled by now. You aren't trying to understand the Russian motivation; this is unhelpful straw-manning and caricaturing.
And othering the Russians with irrational motivations is stupid. As a culture we've passed up too many opportunities to calm the situation down because of a russophobic attitude out of the US. Years of unhinged rhetoric from 2016 onwards turned out to be unhelpful in de-escalating a dangerous situation.
> Countries can be invaded even if they didn't "provoke" it...
I'm not going to quote specific parts but addressing the points you raise from this onwards - nearly nothing justifies war. But what does happen regularly is unfair war. The lesson out of something like the Afghanistan invasion in 2001 is if a major power tells you to do something you have about a month to comply before something unjustified happens and the faster the weak roll over the better it is for them.
If I can swallow that and stay friends with my US friends - which I can - then I can handle almost anything.
> At no point was Russia happy about the USSR member states leaving, and Putin has repeatedly stated that this is the "greatest geopolitical disaster of the last century".
That would be like the British PM lamenting the fall of the British empire. I don't see why believing that would lead to a war or even bad feelings. I do see why NATO expansion into Eastern Europe would though, especially given that with hindsight we know NATO sees Ukraine as an arena to inflict crippling losses on Russia. People in the Russian military probably have sleepless nights worrying about NATO.
And I note you didn't link to speeches by Putin. That'd be wise, it is rare to see a western media outlet accurately representing even western politicians. Not as a partisan thing, but as a blanket failure. It is better to go to the source material.