Russian is a proper noun and therefore is capitalized. If I were to say russians, it would be underlined, meaning it is wrongly spelled. If I were to say Russians however, it is not underlined, so it is the right spelling.
You sir, fail at Grammar pathetically, and completely reiterate my point in saying "Grammar russians", "Whermacht", "third reich" and by having the name, "Gimmedagun".