It does not matter whether there is a majority population of russian-speaking people in Crimea. Russia / USSR gave Crimea to Ukraine, they cannot take it back just like that. A civilized approach would have been to approach the Ukrainian government, asked them for it and offered a pile of money for it (e.g. free gas for 50 years or something like that...) and then had a discussion as civilsed persons. This never happened, and as the Russian logic goes at the moment, we can also argue that:
- St:Petersburg is built on occupied Swedish territory and should be handed back to Sweden.
- Karelia is Finnish (ok Finland is actually Swedish), and should be handed back to Finland.
- Kalingrad should be handed over to Germany, after all it was the center of Prussia, the most german of the german states...
- The Åland islands (who actually had a referendum about joining Sweden, voting 95 % for joining) and is part of Finland should be handed over to Sweden immediately.
- Anschluss was morally justified as the territories that Adolf annexed was "ethnic german".
- Ireland is english-speaking, so England has claim...
- US is English speaking and the Spanish speaking are "oppressing" the English speaking and the UK has moral justification to protect "the English" in the US.
- There are Dutch-speaking people in Belgium, so the NL should invade, they are oppressed by the French-speaking Belgians.
- Three are Flemmish-speaking people in the Netherlands, so Belgium should invade NL to protect the Flemmish/Dutch speaking people from the Frisians.
Where do you draw the line?
The fact is also that Russia signed an agreement leading to the dismantling of the Ukrainian nukes in order for a promise of respecting the integrity of the Ukrainian territory, no one can argue that Russia has not violated this pledge. The fact is that no Russians or Russian-speaking people where oppressed by the government in Ukraine.
There is NO casus belli whatsoever in this case, the Russians are blatantly ignoring international law, their own international commitments (to respect the Ukrainian borders) and are in principle acting like Germany in the 30s.