Russia is now one-man dictatorship, which is the most dangerous form of political system, because it requires from this one man, Putin in this case, a continuous action to prove his legitimacy, and a constant demonstration of his strength.
Putin is a week politician who cannot stay in power by improving economy and life standard -- he's just not smart enough. Russian economy is very weak, so he must show his strength somewhere else. He MUST, otherwise he's gone. He lost his lackey in Ukraine, so it was a perfect moment for him to invide another country having the pretext of "caring about Russian people', which is obviously a humbug.
The sad thing is that majority of Russians support him. It's sad that average people are simply stupid, but Hitler already proved that you can brainwash the masses, even while doing immoral things.
Putin is an immoral man. It's as clear as day. Of course there are many "bad guys" in the world, but Putin is the most dangerous one -- he has nukes and he supports other dictators, in fact every dictator in the world, Bashar al-Assad is still killing people because Putin is behind him.
If the West engages his actions, don't have any illusions that he will stop at eastern Ukraine.
The west must definitely isolate Putin's Russia. Impose sanctions, as much as possible. Give military support (even only weapons) to Ukraine. Don't let them organize international sport events.
Putin is probably the biggest evil in the world at the moment. He's responsible for thousands of deaths. Such man cannot be engaged.