There is no reason to mess with Russia. They are strong and very brave. The Russians have a right to protest and as long as it is non violent, there is no reason that they should not be allowed to protest the mistreatment they feel they have endured. But if the protest is interrupted, history has proven that such civil unrest can and will lead to a revolution.
Yes, Russia is correct that there will be a civil war if Ukraine deploys force against pro Russian demonstrators, because Russia has made it clear that they want to take the Ukraine over again. Crimea went back to Russia and Obama did not do a thing about it. Russia has their sights on Ukraine next.
Russia is not correct in believing that Ukraine could instigate a civil war. The amount of pro-Russian civilians in the Ukraine is outnumbered vastly by the amount of pro-Ukraine citizens. Russia has lost much of its support through its uncalled for annexation of Crimea. Any pro-Russian support in Ukraine is unlikely to garner enough momentum to cause civil war.
I would not say the Ukraine is in the midst of having a Civil War. I would say the Russian government is placing itself in a way that is making Ukrainian citizens even more upset. I think we are seeing a situation develop where the last of the Ukrainian supporters will have to go up against Russia. I wouldn't call this a civil war.