There is nothing respectful about being a mascot. Their sole purpose is to be laughed at, mocked and the subject of jest. These incidents have a negative impact on the self-esteem of Native American children. 
If sports teams really employed Native American culture in their names and imagery as a sign of respect, they would also likely avoid using names like “redskin” and “Indians”, both of which are racial slurs. Nor would they use images like the grinning Chief Wahoo, the red-faced caricature and long-time symbol of the Cleveland Indians baseball team.
Many of the mascots and imagery used was born in an era of racism and bigotry against Native Americans. They were never designed to be a mark of respect. They deliberately perpetuated negative stereotypes and tropes. For example, the term ‘redskin’ was employed in government announcements in the 1800s in which they called for the bloodied scalps of Native Americans and offered bounties as a reward.
George Preston Marshall, the original owner of the Washington Redsk*ns and the one that adopted the name, was a proud segregationist and racist, illustrated by the fact that the Redsk*ns were one of the last NFL teams to integrate.
There is other evidence that illustrates that the use of Native American names and mascots was not borne from a place of respect. At the same time as all-white sports teams were beginning to adopt these names and mascots, Native American children were being educated in schools deliberately designed to crush their native traditions and ‘educate’ the savages.
While indigenous communities were being forced to abandon their culture, all-white, suburban communities were naming their sports teams and designing their mascots around Native American culture. It was a clear example of the majority hijacking the minority’s culture in a negative and damaging way.