I don't have a strong opinion on this issue but I've read arguments like yours many times and they always leave me shaking my head. The terms mentioned in your posts are not derogatory. They are just the names of people and groups - factual ones. (RE: Italian v. Dago)
Redskins is a derogatory term for Native Americans. It's not a tribe. It's just a mean word white people used to call Native Americans while we were busy murdering and kicking them off their land and spreading diseases.
It's not like Apache, Cherokee, Seminole, - or even just the generic, "Indian". It's a mean word with a bad history.
You obviously do have a strong opinion, and it's wrong. If I decide to call myself African-American, and I am not, does it make it any less derogatory to actual African-Americans that I didn't call myself a slur?
In what way does that stupid leprechaun logo Notre Dame uses equate nobility or in what way should it be looked upon as dignified? What about the potbellied, derby-wearing caricature that the mis-pronounced Celtics utilize. How is either of those circumstances not demeaning?
You seem like the quintessential PC pusher, only concerned when it fits whatever agenda you need it to, ever hoping that you will get your gold star from some group you desperately seek validation from, just so you can say, "Yes, I may be a member of ___________ demographic, but I am better than the others of my kind because I have a self loathing tendency that they don't have, and I carry guilt/shame/pride/graciousness/etc... fill in the blanks as it fits for you... which clearly demonstrates that it is okay for you to like me despite my belonging to the lecherous group I was born among."
If people truly wanted the obnoxiously over bearing PC dogma to work, it would apply to all and not select groups, but it doesn't, therefore it will always create a portion of the population that resent it and will continue to perpetuate the types of reactions that lead to resentment among differing groups of peoples, whether they be ethnic, religious, geographic, philosophic or whatever.
The truth is, I don't care if anyone likes my perspective or "Shakes their head" at it. I don't have a need for approval or to get my self worth from others.