It could (many films use the "nig---" word repeatedly, look no further than tarantino) and honestly it should. Racism in the USA was brutal and still continues to this day. We should not try to whitewash it because the word, of all things, offends us.
That sort of mentality is what leads people to try to ban Huckleberry Finn from school libraries, because the depiction itself offends their sensibilities, regardless of the underlying message.
I'll concede Tarantino films are a good example. I think maybe the difference is that Hateful Eight, Jackie Brown, Pulp Fiction, and Django aren't comedies, and it tends to be a lot less casual. I recall most cases in Django being very hateful, used for a purpose. BS dropped it very casually, as if the characters were normal people talking that way every day (which is pretty accurate).
I'm not claiming anything should be whitewashed or censored at all, just that language in a modern context has an effect on how a movie comes across to the audience. I don't think that a modern audience would find it funny without the social atmosphere of the 1970s. I'm making no claims about the quality of the movie itself, as it actually was made. Similarly, if Huck Finn was written today, I do think it would have a really hard time. It works because of the place it has in history.
That sort of mentality is what leads people to try to ban Huckleberry Finn from school libraries, because the depiction itself offends their sensibilities, regardless of the underlying message.