Re: Try seeing it from the Kremlin's point of view
As stated above, your arguments eem to be straying into the field of Russia can do what the hell it likes because it's a major power.
And the answer to that is, up to a point. We should certainly take account of Russia's legitimate national interests. However they don't get a free pass to do whatever the hell they like.
I'm no fan of international law. Because it's semi-fictional, has little democratic legitimacy, and doesn't have particularly effective mechanisms to make it work. However, it's what we've got. And it's a good basis for international behaviour.
Iraq gets to be legal, because Iraq was in breach of the ceasefire terms from when they were thrown out of Kuwait in 91. As well as many subsequent ones. Also they made it impossible for the weapons inspectors to find the weapons that it turns out weren't there - or verify whatever actually happened to them. That resolution only got through with weasel words - from memory it specified serious consequences rather than grave consequences (which is the normal legal term adopted by the UNSC for resolutions it backs up with military force). However it was clear what the US and UK meant by that resolution, so if France and Russia had really objected, they should have vetoed, not just watered down that word. So there was a perfectly arguable legal case, without a court to argue it in, Saddam was given nearly a year to negotiate - and the consequences of not doing so were made totally plain. Whatever you may think of the invasion it is totally different to what happened in Crimea, where Russia didn't attempt to negotiate, had no even vague legal justification, and not even a reasonable cause to resort to military force.
Even if I accepted that Russia has a legal right to use military force to retain the Sevastopol base (which it didn't), there had been no threat to it. Even when Russia cut off Ukraine's gas supplies in Winter, no threat was made to that base. U:kraine did threaten not to renew the lease in future, and that was one of the bits of leverage that got a new deal agreed.
Also, Putin has spent years lecturing everyone about non-interference in soveriegn states. That was their argument to continue to allow the Serbs to massacre the population of Kosovo, and to allow the Syrian government to continue the slaughter.
Had there been serious attacks on the Russian speaking population of Crimea, they would have had a legitimate reason to intervene. Even though it would be illegal without UN backing. As we did in Kosovo. Although I doubt there would have been a Security Council veto under those circumstances.
Basically it would cost Russia a load to build a new naval base. And that would be just their tough shit. If they're unable to negotiate to keep it.
One of the other massive problems this has created is that Russia specifically violated a treaty to respect the terriorial integrity of Ukraine. This is hugely important. As how do we negotiate with Russia now? There are plenty of other places that they might choose to invade, using the excuse of a Russian population left over from Soviet days. Including Eastern Ukraine (where they are currently massing forces). Do we allow this? We certainly can't trust them to keep their word. After all Putin said they weren't planning to invade the day before he did it.
We're treaty-bound to defend the Baltic states. We let them and Poland into NATO. We either need to dissolve NATO and admit we don't care, or signal to the Russian government that we're serious. Otherwise we could end up getting ourselves into a really stupid war. If NATO doesn't want to do the job, then I'd imagine that there's going to be an awful lot of nuclear scientists getting very busy in places like Ukraine and Poland.
I'm not a Putin apologist. Or a supporter of armed aggression. I'm just an ordinary bod who's prepared to make the effort to see both sides of the argument
There are no both sides of this argument. Russia's invasion and annexation of a neighbouring country is entirely illegitimate. Both legally and morally. It was pure, naked armed aggression. As the strategy worked, they've continued it, by mobilising troops on Ukraine's Eastern borders and threatening another invasion to peel off more of the Russian speaking bits. Where Russians are in a minority. This is proper 1930s style nationalist miltary aggression. Fortunately without the bits about master races and genocide. The question we need to known is what does Putin's regime want. And will the appetite grow with the eating? Do they have some limited objectives, which can be reasonably accommodated, or quietly ignored where realpolitik suggests it's better to give in? Or has getting away with the invasions of Georgia and Chechenya persuaded them that they can recreate some sort of Russian empire, like the good old days of the Soviet Union. Or do they really believe in all that crap about things being better in the good old Soviet days - and want to re-create it?
I remember reading a piece by Robert Service about 3-4 years ago. Where he compared 1930s Germany and Russia now. There's this feeling of the ex-KGB types running the place that they didn't lose the Cold War. That nasty Gorbachev betrayed them. He went all soft, and collapsed the USSR - even though they were superior to their Western counterparts. In Germany it was the stab in the back. The army didn't lose in France, so Versailles was somehow 'not fair'. Even though it was less harsh than what Germany imposed on France in 1870 - and what they were planning to impose on France in 1914. Instead there was this myth amongst the German nationalists that the socialists and jews on the home front lost the war for them.
I dimissed it at the time, as an old Cold Warrior who couldn't forget the past. And Putin as too rational to buy into all that rubbish, and the dangerous consequences it could lead to. Now I'm not so sure, and I'm a lot more worried. And Putin seems a lot less rational, predicable and measured in his actions than he did 5 years ago.