The rest of your post is just more trying to shift blame onto Ukraine. They're a sovereign country, they should be able to ally with any other country they want without being invaded by their neighbor.
Sure, I agree they should be allowed to. But I also think it's reckless to actually do it.

Don't you find it amusing that you'll call UK withdrawal from the EU a stupid decision, economic suicide and whatnot, laugh in my face when I talk about sovereignty, and now you tell me that you respect Ukraine's sovereign right to infuriate their mentally unstable superpower enemy? I find it hilarious.

This line about the Black Sea is wrong. The only value the Black Sea has is if you can ship out of it into the Mediterranean. It doesn't matter if you own all the ports on the Black Sea if NATO holds the straights in Turkey. Guess who belongs to NATO?
Yeah there's also Bulgaria, so NATO already has access to the Black Sea. But there's more to it than just military. There's a fuck load of gas under the sea, and whoever controls Crimea controls the majority of that gas.

NATO do actually have trouble getting ships into the Black Sea. Russia employ treaty loopholes, for example the treaty that governs the Istanbul straight. There's a limit to how many military ships can be in there at any one time, so Russia maintains a permanent presence in there to reduce that further. This is why Turkey are planning on building a canal, to bypass this treaty.

It seems to me that Putin wants to stop Ukraine from having access to most of the Black Sea gas reserves, since if Ukraine can fully exploit these reserves, that will be a challenge to Russia's energy sector. And that's hitting the powerful elite in Russia.