I think: ACCEPTABLE.
See, this really is nothing very original, the story of the old Russian bear going bad again has been used as an excuse to kill Russians in many games before. (I can even think of 3 games I actually have that use this storyline: EF2000, EF Typhoon, Ghost Recon)
Of course, this is only a general story, something that is a start-up point for a campaign. It could still be a good background for a campaign if you develope the story during the campaign with some twists and turns and tension.