I wouldnt call a native american a Redskin, because it has no meaning to me. Its just the name of a football team. I wouldn't necessarily call them native americans either because American is a European name, not a race. If you want to label people by physical characteristics, native americans are actually Asian, specifically Mongol Chinese, from what i understand. Perhaps the correct term is Mongol-American?
However since the point of this thread to somehow convince us that Redskin is derogatory, I dont see any proof of that in its use as the name of a football team, thus its ok. Intent is what matters.