The first protests occured in 1968 by the National Congress of American Indians ie after the civil rights movement made it relatively safe to oppose the white man. The fact the white man has ignored these protests for 45 years doesn't make the term any more appropriate. It just means that people will accept ignorance/racism because of tradition.
And in case you didn't know, from 1930 to the 1960s, America was openly racist. So no, people didn't just wake up 80 years later and determine Redskin was offensive. It was always offensive but the racists in the 1930s to 1960s just didn't give a shit well because they were racist. You might as well ask why the KKK never protested the use of the word N***er. Sheer genius.
It's like you are completely oblivious to American history. Like you think everyone including Native Americans were living in bliss and loved the name and only now in 2013 decided it was a problem.