actually...when an american jew says szchwartze he means nigger. It does mean black, yes, and that is the origin of the word, but when a jew says szchwartze he means nigger. it's the same way a jew can call a white girl a white girl, but if he calls her a shiksa it's with the intention of prejudice, same thing when calling non-jews goyim. no one uses only yiddish anymore, it's virtually extinct. Only hasids and geriatrics use it, and only on certain occasions (when they dont want anyone else, especially their kids, to know what they are saying). when someone uses a term like shiksa or goy in an everyday conversation, they mean it like they dont like them, like they are trying to put them down and make them lesser people. Not that that's a bad thing, goyim ARE lesser people....but thats besides the point.
around NYC, blacks know this, and when they hear szchwartze they get pretty mad. When i was in 4th grade, i heard my grandpa point to some black guys and say "look at those szhwartze, they all look and act like a bunch of monkeys" on the way to hebrew school. The class went out to central park to play in the playground, and there were a couple black guys hanging around there too. I decided to come up to my teacher, who was sitting not far from the black guys, and asked her "what's a szchwartze?" pretty loudly. The black guys immediately turned and started, giving me and the teacher a long, hard, evil look. the teacher didnt say anything, got up, got the class together, and left the playground quickly. When we got back to the school, the teacher with the school principal gave me a lecture about the definition of the word, and why i should be careful when using it because "there might be blacks listening and they might not be very happy to hear that word".
Later in my life...a few years ago...i was walking through queens and there were these two rabbis walking and talking, obviously discussing blacks because they were sprinkling the word throughout every sentence. they brushed up against some gangster-looking black guys and as they pushed passed one of them muttered guess what in yiddish. That rabbi was knocked the fuck out immediately.
Jews in NYC are racist as fuck. maybe you should look into the decades-long tension (sometimes escalating into riots) that has been occuring between the jewish and black community throughout brooklyn and along the fringe between the upper west side of manhattan and harlem. it's gotten pretty fucking ugly before.