I don't think it's as conscious as that. I think the bias is systemic; it reflects the prejudices of the people who work at the BBC - i.e. a middle-class, metropolitan, broadly-liberal set - and the more remote a subject the less likely it is to be treated with impartiality or objectivity ("remoteness" usually being a measure of distance outside the M25).
BBC News is a self-contained department at the BBC. Documentaries tend to be commissioned and produced by specific channels, so there's a bit more scope for plurality there. Not much, but a bit.But they are not totally biased against Russia - for example there was a really awesome BBC nature program called "Wild Russia" that was totally free of prejudice, just showing awesome views, animals and cool locations in Russia. But as for politics, their view is pretty clear.