The list of criminal acts I pointed out are more than mere 'tensions', OP. And you haven't addressed my point that Russia is imposing war on us, whether we want it or not.
The UK is not part of the bizarre 'American Empire' you seem to have invented. NATO was established to counter the threat posed by Russia - it's a defensive alliance, not a group of violent, aggressive warmongers. NATO has not attacked or invaded Russia.
https://www.nato.int/cps/ra/natohq/115204.htm
Russia is the one who has broken international law by invading another sovereign state. And if they were genuinely worried about NATO expansion, they'd live a peaceful existance within their own borders. It's blatantly obvious to even the most politically illiterate that the quickest way to expand NATO is to invade other nations. No doubt Finland and Sweden would still be neutral had Russia not invaded Ukraine.
I don't see anyone MAKING Russia their mortal enemy and I have yet to hear a head of state call Russia their mortal enemy. I see Russia seeking power, land and wealth through the violent invasion of another nation state; kidnapping thousands of their children and sending them to "reducation" camps within Russia, brainwashing them into thinking their parents gave them away or didn't want them; attempting to commit genocide through the murder of innocent civilians and sending an influx of Russians to outnumber locals. I could go on, but instead I'll point you to the many news articles and books detailing their atrocities.
No Ukrainian territory has been permanently lost to Russia yet. They and the rest of Europe will keep fighting.
I assume your dismissive remarks about "some of it was already leased to Russia anyway" refer to the Partition Treaty and the controversial Kharkiv Pact, which Russia effectively blackmailed Ukraine into agreeing by pushing up the price of gas to unaffordable levels? If that is what you are referring to, Russia unilaterally terminated the agreement on 31 March 2014, after their invasion and illegal annexation of Crimea.
I agree that the UK should not have allowed Russian oligarchs to wash their dirty money here, but I fail to see what that has to do with your post about not wanting to go to war.
What do you mean, "we should stop relying on Russia to defend us"? Who is us? Fear not, I don't believe the UK or any of their allies will be expecting Russia to leap to their defence any time soon.
"We need to stop throwing people at this war". Again, who is "we"? I see Ukrainians fighting for their lives. I see Putin "throwing people" at HIS war.
I don't see anyone getting hysterical - except, perhaps, some of the people writing vague nonsense posts, with none of their points backed up by facts. I see those people get hysterical when people point out the holes in their arguments (with facts), then petulant when they lack the debating skills to argue back effectively.
NATO and the West have consistently tried diplomatic solutions with Russia - as has Ukraine. Russia has proceeded with their war. One cannot negotiate with an enemy that does not wish to negotiate.