Here's Costas' take:
“Think for a moment about the term ‘Redskins’ and how it truly differs from all the others,” Costas said regarding the Washington name and other team names referring generally to Native Americans or specifically to tribes. “Ask yourself what the equivalent would be, if directed African-Americans. Hispanics. Asians. Or members of any other ethnic group. When considered that way, ‘Redskins’ can’t possibly honor a heritage, or a noble character trait, nor can it possibly be considered a neutral term.
“It is an insult, a slur, no matter now benign the present-day intent,” Costas added. “It is fair to say that for a long time now, and certainly in 2013, no offense has been intended, but if you take a step back, isn’t it clear to see how offense might legitimately be taken?”