Dude, are you serious? How is the question of Native American sovereignty relevant?
Honestly, the imbecilic arguments people make in defense of keeping a racial slur as the name of an NFL team are more disturbing than the name itself. Everyone realizes the team-name is offensive and that it points to one of the darkest most troubling parts of our history -- interestingly, a part that most Americans still refuse to recognize as the foundational event of our history. It's a stain on the culture professional sports because the genocide of native peoples on this continent remains a stain on American life and culture. You can trot out as many comparative fallacies as you want, that's not going to change.
One of the lamest consequences of today's multiculturalist rhetoric is the idea that "racism" is somehow a generic condition -- like the way people talk about "cancer" (also mistakenly). So everyone gets to claim they don't have the racism disease while continuing to ignore the role that race place in their everyday perspectives. Racist policies, attitudes, and institutions always have particular histories and particular targets. The fact that we would more or less have consensus that "Niggers" or "Yids" would be unacceptable as team names while "Redskins" remains acceptable merely indicates the particular sort of racism that most Americans still practice.
Maybe Dave is trying to "thread the needle," but in the end trying to force that camel through only obfuscates an issue that is about as clear as cultural issues ever get. It's painfully obvious: anything but straightforward opposition to "Redskins" amounts to a racist position. Deal with it.