Interesting theory but very wrong. Belarus does NOT means "White Russia" but "White Rus". Their people should be called Belarusians. Foreigners who have not enough knowledge about history of the region often confuse Rus and Russia, two diffrent names. Also Russian nationalists pushing this wrong name from well known reasons.
http://www.pravapis.org/art_white_russia.as http://www.pravapis.org/art_belarusian_adjective.asp