Your poll was part of a 2004 national election survey and it didn't verify the race of those who claimed to be Indians. If it was a stand alone poll that polled only native Americans then you might have something....but you don't. So yes, your poll was deeply flawed.
"...The survey most frequently cited by opponents of change was performed in
2004 as part of the National Annenberg Election Survey. Among other questions regarding election year issues, respondents from the 48 continental U.S. states were asked: "The professional football team in Washington calls itself the Washington Redskins. As a Native American, do you find that name offensive or doesn't it bother you?"
The problem of individuals claiming to be Native American when they are not is well known in academic research, limiting the value of public opinion polls of the mascot issue.[230]...."
Washington Redskins name controversy - Wikipedia, the free encyclopedia
Your poll is flawed on an even deeper level. It suggests that if popular opinion supports prejudice and racism (or racist mascots) then the matter is settled when in fact it isn't.
"...It suggests that popular opinion can settle troubling questions about prejudice, power, and privilege. Hence, if the majority support mascots (or racial segregation or sexual harassment), then such symbols and practices are acceptable. And worse, [it] asserts that if members of marginalized and oppressed groups consent to their marginalization and oppression, then everything is OK. If most Blacks supported racial segregation, would it be a justifiable system? If most women saw nothing wrong with sexual harassment, would we not still want to suggest such actions were reprehensible and problematic? Unfortunately, in the end, "The Indian Wars" encourages Americans to avoid thinking critically about the history and significance of race....."
American Indian Sports Team Mascots