It's about who is saying what to who. A guy could say N_____ to someone he knows as a term of connection, as a friend, and the other person wouldn't think anything of it. It would just be another way of greeting or general speech. That can go with any word or term that is found offensive. But if the same person walked up to a stranger and called them something, even if it wasn't meant as a slur or insult, would likely be taken as such. It really depends on who you speak to.
Also, I agree that having a month dedicated to "Black History" is racist. I remember last year some celebrity, I think Samuel Jackson, had a fit because everyone should remember their history all the time. I had more to say, but the prospect of food has thrown my train of thought off.