Over the years, I've had a number of people tell me that the word "nigger" did not actually apply exclusively to black people. Instead, they said, this word applied to "ignorant" people, and so therefore, if they used it, they were somehow not being racist. Somehow, it's appropriate that the alleged synonym for the word is "ignorant".
Upon reading this article from the Online Etymology Dictionary, anyone can plainly see where the word "nigger" came from. I am unsure how anyone could confuse the issue.
My point is this: "nigger" is a racist term. It is meant as a derogatory term that is ascribed to a set of physical characteristics. Don't think that because you use it to mean "ignorant person" or "lazy person" that you are somehow not being racist. When you use a term that means "black person" to call a person lazy, you are saying that black people are lazy. You are being racist.
Don't be ignorant. Educate yourself. When you choose to use a new vocabulary, be certain that the words are actually defined as you think they are defined. And don't go by your buddy's definition, because he's likely to be as ignorant as you.