Generally, I'd agree with that sentiment. However, what path forward would provide the best way out of the situation and discourage further conflict in the region?

When we look at the lead up to WW2, we see a build-up of tension by Germany and attempted appeasement by the other major powers in an effort to avoid another breakout of war in Europe, only a few decades after the first great war ravaged these nations.

Notable events:

• Remilitarization of the Rhineland (Mar 1936) -- this was a clear power move and violation of the Treaty of Versailles that ended WW1. With no real reaction from the France/Britain, this was a clear indication to Hitler he could continue to push things much further.
• Anschluss (Annexation of Austria, Mar 1938) - Germany was prepared to take Austria by force, but managed to do so with only the threat of violence. This was also against the Treaty of Versailles and also had no real reaction from the Allied powers.
• Sudetenland conquest (Sept 1938) - Germany pressures Czechoslovakia for pieces of it's territory that border Germany. British PM finally gets involved, allowing the exchange of territory for a promise of peace. This is the famous " Peace for our time declaration.
• Annexation of territory from Lithuania (Mar 1939) - Lithuania pressed to give up territory under threat of war.
• Czech/Slovokia split and occupation/control (Mar 1939) - Under further pressure and threat of invasion, Czechoslovakia split and both come under German control.
• Invasion of Poland by Germany and USSR (Sept 1939) - First open conflict. France and Britain declare war on Germany, roughly a year after the "Peace for our time" negotiations/declaration that clearly made a difference!

As you can see, in the build-up to WW2, the European powers that opposed German expansion sought alternatives. They even allowed Germany to push its weight around on its neighbors, taking territory from others, and consolidating power. By the time the great powers were forced into conflict by open war in Poland, they were no longer in a position to hope to control Germany at all, doubly so with their apparent new cooperation with the USSR.

Knowing what happened, it's easy to see that any intervention by France and/or Britain, whether it sparked violence or not, in the early days of German aggression would have almost certainly led to a less powerful Germany, perhaps one that could not have taken over most of Europe so easily.

I think the key take away from all of this is that, modern nations that have a desire for conquest are a danger to all. They are not to be believed, they should not be appeased, they should not be rewarded. Any violence against free nations should be resisted, supported by all free nations, but without escalation to full-blown nuclear war.

The danger of washing our hands of the conflict and saying something like, "Violence bad. End the war. They can have Ukraine/Donetsk/whatever." is that Russia won't stop there. They'll get bigger, stronger, and move on to the next target when they're ready.

The horrible part about all of this is that the apparent best way to keep long-term violence down is to continue the fighting now. The longer the conflict continues, and the more humiliated Russia becomes, the less likely Russia will chose to do a similar invasion in the future.