Zelenksy was openly threatening to host nuclear weapons for Nato on the eve of the invasion
Do you understand that there's a difference between hosting weapons in your country and (let's say) invading another country and (for example) launching missile strikes at civilians? (And can i just say? That Wikipedia page just keeps going and going.)
Let's also not forget about Russia continuously threatening to nuke Ukraine without commensurate nuclear threat from the other side. (They just keep doing it!)
Really, if we go back to the start of this (the pre-Crimea days), Ukraine had two futures. In one, it grew closer to Russia and came under the Russian sphere of influence. In the other, it grew closer to the West likewise. It was leaning in the direction of the West, but when Russia attacked it sure as hell pushed hard in that direction. Now everyone in the region wants to get in on NATO and Russia is claiming that's "provocation". That's nonsense, and it's shameful and pretty slimy to carry water for their nonsense.
They didn’t invade; they were already there...
I dunno how to tell you this but the entirety of Crimea is not Russia's private naval base. No, not even if Vladimir Putin really wants it.
...western backed coup...
You mean the Revolution of Dignity??? That's what you're talking about here, right?
Well that’s just fucking stupid. Peace treaties don’t count if they came after a war?
No, that's not the argument. The argument is that whether or not they broke a cease fire has no bearing on whether past or future invasions of their country are justified. The Russian invasion was unjustified from the start. It doesn't magically become justified because Russia claims the other side broke a peace treaty. Russia could withdraw at any time. They could have even withdrawn to Crimea and probably been fine. Again, they claimed to not even be party to the treaty!
These are some pretty shameful arguments, overall.