When history books and literature is written, what category of characters do you think Putin will be listed along with as a state leader?

He's very similar to pre-Holocaust Hitler. What Russia has been doing in the Ukraine pre-invasion is very similar to what Nazi Germany did in the Sudetenland (Czechoslovakia) - flood it with your own people, then claim annexation by the will of those people.

"Flood it with your own people?" If I'm not misunderstanding you, you seem to ignore that Crimea had been Russian for quite a long time. Khrushchev transferred it to Ukraine in 1954; practically, insofar as I can comprehend it, as a sign of good faith.

And if we indeed foresaw the signs of another Hitler on the rise, we sure didn't do much to prevent this sequence of events, did we?

I didn't mention Crimea, which was historically Russian and remains ethnically so. Kruschchev shifted it into the Ukrainian SSR for numerical reasons, while it was undr central control it hardly mattered. It should have reverted when the Soviet Union was Balkanized.
The Donbors region, on the other hand, had never been part of Russia proper, ethnic Russians have been moving into the area for over a decade (since the Orange Revolution tossed the pro-Russian Yanukovych out the first time, it's unfathomable how this scandal-ridden crook got elected again) and over 700,000 Russian passports were issued in the city of Donetsk alone. Sudetenland II. And paralleling the rise of Hitler in another way, nobody did Jack about it then either. We came, we saw, we concurred.

All fair points, and part of the overarching ugliness. That part about "annexation by the will" of those supposed locals, though, does only seem to make up a portion of Putin's arguments (if I may call them that). To me, it seems that the main issue is NATO's potentially endless encroachment, across the world. Some other nations may also feel like the longer it goes on, the more precarious their situation becomes. It's one thing for a country to join the EU - but an entirely different matter when foreign militaries come into play...

Anyhow, the point of my original post was this: in yelling "he's Hitler, he's Hitler," are we doing anything at all to bring some much-needed perspective to the problems ahead?

Anyhow, the point of my original post was this: in yelling "he's Hitler, he's Hitler," are we doing anything at all to bring some much-needed perspective to the problems ahead?

Of course not.
That would require investing in 2 things it is rare for governments to do.
1 - People with an understanding of history, beyond the drivel taught in public schools.
2 - People willing to pursue diplomatic solutions to future conflicts before we actually get to a point of conflict.

Sadly true. In your answer, you said that Hitler and Stalin receive passing mentions in American schools? 

As for diplomatic solutions... I am obviously speaking as an utter layman, but would it have been too much for NATO to agree not to come any closer to Moscow? (I disagree with the suggestion that physical proximity no longer matters considering modern military technology.) Hopefully, that's still on the table (even if there now exists more reason for the contrary), and a way of ending this war - sooner rather than later.

In your answer, you said that Hitler and Stalin receive passing mentions in American schools? 

Unfortunately, American public schools try to cram all history in a single school year.  Not that they don't teach multiple school years of history, but every year is the same.  The teacher tries to get through a textbook that covers all American history.  (A better method would be to divide it up into eras, and each era be taught in a different school year.)  Even so-called World History classes in public school tend to be American-centric.  Nor do they even attempt for students to understand the causes of history.

Honestly, I sometimes think it would be better if the teachers just threw out the textbooks and showed History Channel documentaries.

Though in 1997, Russia formalized giving Crimea to Ukraine.

Under the terms of the agreements:

The Soviet Black Sea Fleet that was headquartered in the Crimean Peninsula at the time, was partitioned between Russia (81.7%) and Ukraine (18.3%). In exchange, Russia agreed to pay $526 million as a compensation for its part of the divided fleet. 
Ukraine agreed to lease Crimean naval facilities to Russia for 20 years until 2017, with an automatic 5 years renewal option. Russia would pay Ukraine $97 million annually for leasing Crimean bases. This payment was deducted from the cost of Russian gas provided and billed to Ukraine. The basing rules were set in a status of forces agreement, namely Agreement between Ukraine and the Russian Federation on the Status and Conditions of the Stationing of the Black Sea Fleet [BSF] on the territory of Ukraine. The treaty also allowed Russia to maintain up to 25,000 troops, 24 artillery systems, 132 armored vehicles, and 22 military planes on the Crimean Peninsula.

Russia was bound to "respect the sovereignty of Ukraine, honor its legislation and preclude interference in the internal affairs of Ukraine" and, furthermore, Russian military personnel had to show their "military identification cards" when crossing the Ukrainian-Russian border; Russian forces could operate "beyond their deployment sites" only after "coordination with the competent agencies of Ukraine."

A fourth agreement, the Kharkiv Pact, was signed on 21 April 2010 and extended the lease until 2042 (with possibility of renewal for an additional five years) in exchange for a multiyear discounted contract to provide Ukraine with Russian natural gas.