I’ve encountered it a few times and I’ve been told (by them) that it’s not racist. So is it a common thing, any reason why they say it?
I have also been told that the term is not racist by the 20 something white American males. The African American people that I know do not agree.
No. Maybe some specific subculture finds this acceptable (hip hop music scene?), but in general it is going to get you in trouble.
A key point is - do any of the white american males saying “nigga” use the word in front of actual black people? Or do they just say it amongst themselves because it’s taboo?
no
Yes. I made a thread not too long ago discussing this phenomenon among the gaming community here.
Because they are douchebags who get off on feeling that they’re cool enough to say naughty words but don’t want to own up to their privilege or racism.
I never hear my 20-something white male son or his friends say it, and they’re all gamers. They are more into movie/TV show/game references, memes and jokes.
The last guy who said it, last night, took umbrage when I said he wouldn’t say it to a black person. He also said that nigga and nigger are different words. One is racist, the other is not according to the linguist. He also took uber-umbrage at me accusing him of being a racist.
He may not be racist, in which case he is a clueless twit. His call.
Yeah, I would guess that the vast majority of the set {white American 20-something males who use the word ‘nigga’ amongst themselves but not in front of black people} are actually just morons, not racists - although some are undoubtedly morons and racists. But the guy in your example probably took umbrage because he thought you were impugning his courage, suggesting that he was afraid to use the word around black people. Then the uber-umbrage when he thought you were calling him a racist is pretty much the typcial response by anyone accused of racisim, even actual racists (who are always morons.) That said, I suspect the guy in the example actually wouldn’t use the word around black people, and the umbrage was an attempt to get you to shut up before you called on him to prove it.
If that makes any sense.
Because for some people, being accused of racism / homophobia / sexism is worse than racism / homophobia / sexism. That’s why it’s so hard to call people out on this shit. They get defensive, and make it all about them and what good people they are, and aren’t you so very mean for implying that they might have said something offensive! Why, *they have black friends and they voted for Obama and everything. *
Whites can’t use the word period. You can’t pull it off.
It’s like “I can say my mother is a jerk, but no one else can say bad things about my mother.”
Same principle.
Although I noticed other minorities like Latinos can use it and get away with it, but not whites 
well, I heard it a lot when I was in high school, amongst 16-18-year-old white males (but only amongst each other and only after carefully checking for the presence of, you know, actual black people) so I assume some of them carried on with it a couple more years.
I heard it a lot in certain social circles in my early 20s. It’s pretty much what you think - sheltered white kids who desperately want to be part of hip-hop culture. Sheltered as they may be, most are smart enough to shut up around actual people of color.
I think it’s a natural progression from listening to hip-hop, memorizing the words, and then aping the language with their friends.