“The native language of 74.9% of the population of the Donetsk region is Russian, compared with 24.1% Ukrainian.”
http://en.wikipedia.org/wiki/Donetsk
Just like for 30% in Kiev, language is not a major factor here, in many other areas with majority of Russian speakers there’s no sign of separatism, you could as well claim that Taiwan should be annexed by the PRC because people over there speak Chinese.
Hmmmmm:
As of the Ukrainian National Census, 2001, the ethnic groups within the Donetsk Oblast are: Ukrainians 2,744,100 (56.9%), Russians 1,844,400 (38.2%), Greeks 77,500 (1.6%), Belarusians 44,500 (0.9%), others (2.3%).[7]