The United States attacked a sovereign state called Serbia during this "peace on the continent for almost eighty years" -- somehow that doesn't get counted as an interruption of peace in your view.
The United States then carved territory out of that country Serbia and declared it to be a new independent country Kosovo. When the United States did this along with NATO, they literally scrapped the part of NATO's founding charter which declared NATO to be a purely defensive organization that will only fight on the soil of its own member states to defend them. At that point, NATO ceased to be a defensive organization and became a militarily expansionist organization. They then said, "don't worry, this is just temporary, Kosovo won't actually become a NATO member." Right now, Kosovo is using the Ukraine crisis to demand being made a NATO member. Kosovo isn't even located near Ukraine. Their argument is ...
Your quite right that the international order has been challenged many times, as well as has been the sovereignty of many countries. Poland, Hungry, Czechoslovakia, Georgia, etc. come to mind. However, whatever the wisdom of NATO's decision to become entangled in the Balkans (which seemed very unwise to me at the time) your comparison suffers from your lack of knowledge.
Kosovo can request and reason as it likes, it has no relevancy to NATO's decision to assist a victim of naked aggression conducted by a declared enemy of its current members. Nato's actions against Serbian ethnic cleansing had nothing to do turning Serbia into an unwilling EU member or puppet state. The Balkans were already at war between various nations. refugees were spilling over international borders, ethnic cleansing underway, and Serbia was the primary cause. This wasn't remotely comparable to Putin's intentional aggression against a peaceful state, conquest and annexation of territory, and sponsorship of so-called "separatists" as a mercenary force and Russian proxy.
It's very obvious that Ukraine is not a united society, despite your desire to turn a blind eye to this. One third of the country's population identifies as ethnically Russian. Why are these important things missing from your perspective? The Yanuckovitch govt was the democratically elected govt, and was thrown out by a street mob through Capital Insurrection street coup. Those people declared themselves to be the govt and then proceeded to outlaw Russian language and culture. This triggered Russia's military response to seize Russian-majority eastern Ukraine. Crimea didn't have to be seized, since it was already in Russian hands, just like Guantanamo is in US hands. So Zelensky is not some all-Ukrainian leader -- he represented a leadership that is ethnically skewed and not a representative govt like the one it threw out. I think it's very clear that 2014 was the year democracy was overthrown in Ukraine. And when you argue with them about it, they only vaguely reply "Well, what did you expect us to do when the govt was preventing us from joining EU?" That's not a justification for overthrowing a democratically elected govt.
Actually, it's very obvious you are parroting a party line, a rationalization for your antipathy for the west and sympathy for a strongman bully. Yes, about 30 percent of the country use Russian as their first language but about half those are also loyal to a Ukranian state, not Russia. And the Yan. govt was barely elected under his promise to support and sign EU membership, the conclusion of five years of hard negotiations with the EU. Days before he was to sign, he was summoned to meet Putin who then promised to tear up contracts with Eastern Ukranian manufacturers and put hundreds of thousands of Yan. supporters out of work.
Yan. broke his promise, angry voters turned out, the democratic parliament tossed him out, and that was that. The fraud was nominally democratically elected and democratically removed. Putin's blackmail backfired. That should be the end of story.
And no, the Russian language was not trying to be outlawed. The law of 2012 was trying to be repealed to return to the prior law, and then a new law made. Ukrainian would be the language used by the State (as already in their constitution) and Russian also used wherever those speakers were greater than 10 percent of the population.
And no, Crimea was not in Russia's hands, it was predominately Russian speaking in population but a part of Ukraine. The Russian naval base was "Guantanamo", Crimea as a whole was Cuba. Putin decided to invade "Cuba" because he wasn't happy with just a base.
And what do I expect people to do when an agent of a foreign power gains office by fraud? I expect the government to use its power of impeachment to toss the guy out. And, in the context of the people's rage, they did.