Apparently, there's a show on MTV called Jersey Shore. I have no interest in the show, but in the ads for the show, the guys refer to themselves as "Guidos" and a girl calls herself a "Guida". I talked to someone about this and we disagreed as to whether these were slurs or not.

I also fully get that there are some words (no examples, sorry) that people of a certain race/ethnicity/culture can call themselves but no outsider better dare speak.

So what is it? Are these offensive terms always, sometimes, never?

TIA, and please realize that I don't mean to insult anyone with this post. I myself am Italian, albeit one detatched from the American East Coast.