controversy on mascots

Redskins, Savages, Chippewas, Seminole...

Why are these names so offensive to some groups?

According to the article on "The Final Call", The bill called the Non-Disparagement of Native American Personsor Peoples in Trademark Registration Act of 2013 was introduced in the House of Representatives in March 21. If passed,  the Washington football team of its trademarked name would be stripped and put a stop to its exclusive profiteering from using the racist slur in its logo on sweatshirts, tee shirts, caps, coffee mugs and dozens of other products flooding the market.

The reason why this bill was introduced is because there are plenty of controversy over these team names and mascots because various groups with American Indian background view them as offensive and disparaging. Some groups view them as offensive because many of them do not know about the innocent history of the word redskin. According to Smithsonian linguist Ives Doggard, European settlers in the 18^th century had adopted the term from Native Americans. They used "red skin" to describe themselves and it was generally to name themselves, not to insult themselves. However, over time, it became less innocent and more ambiguous. And the fact that the history of the word "red skin" is innocent cannot be an excuse. So the term should not be used anymore because time has passed now and it is not like that 'innocent history' make any groups feel better. 
One of the issues is the use of these offensive names as school mascot for elementary schools, middle schools, and high schools.  It is a bigger problem for the young students because they say these names without knowing their actual meanings and what they are referring to.  It might be better to say these things without thinking about the demeaning and disparaging meaning of the terms but it is still offensive and disparaging to various groups with American Indian background.  The meaning does not go away even if the word is used more benignly.
 There are many names, terms, and words that are made to be offensive and racism toward different groups with different racial backgrounds.  Sometimes those words are used as slangs and as nicknames with close friends or among the same races.  However, it is wrong to name sports teams' names with racist words because they are supposed to be representing each States and the United States of America.  Fans from other countries who know the names are probably calling the team names without even knowing the history or background. This also could be offensive to those groups who view them as disparaging because people from other countries say these names without knowing the meaning which is disrespectful.  Therefore, there the bill, the Non-Disparagement of Native American Persons or Peoples in Trademark Registration Act of 2013, which would prohibit any future trademarks that use the offensive term, should be passed.