Internal State Department cables from the embassy in Moscow say that entire Russian security and political establishment viewed it as a critical national security threat.
In particular, take a look at this cable: https://wikileaks.org/plusd/cables/08MOSCOW265_a.html. Here's an excerpt:
> Ukraine and Georgia's NATO aspirations not only touch a raw nerve in Russia, they engender serious concerns about the consequences for stability in the region. Not only does Russia perceive encirclement, and efforts to undermine Russia's influence in the region, but it also fears unpredictable and uncontrolled consequences which would seriously affect Russian security interests. Experts tell us that Russia is particularly worried that the strong divisions in Ukraine over NATO membership, with much of the ethnic-Russian community against membership, could lead to a major split, involving violence or at worst, civil war. In that eventuality, Russia would have to decide whether to intervene; a decision Russia does not want to have to face.
There are warnings throughout the cable that Russia may decide to invade Ukraine over the issue of NATO enlargement. In other words, the claim that this is just a Russian talking point is itself just a talking point.