Well, they are at least using that as their justification. They may have ulterior motives (as most nations do), but this is one of the primary goals. I think they want Crimea for strategic reasons, and they are looking to set up a buffer zone between Russia and NATO countries. Donbass as an independent nation would serve that purpose. While they are there, they are looking to destroy the infrastructure of Ukraine to make it a less desirable staging area for NATO defenses.

---