As I remember, we are always asked not to use the words NEGRO and NEGRE when talking with a black man.
But in a movie, I saw that blacks call each other with this word, and none of them gets angry of this. They used it in joking, in daily conversation, and nearly in every field, and none of them was thinking about punishing the others, although my tour guide told me: NEVER CALL A BLACK BY NEGRO OR NEGRE.
What's going on? Do they get angry by this word only by white men???
do they have this sensitiveness only for white guys?
The word you're talking about has been used as a term of abuse for a long time and it continues to be a "taboo" word, i.e. a word any learner of ESL should avoid. However, among some black speakers it has been claimed and used in a positive way. To quote the Merriam-Webster online dictionary:
"usage: Nigger in senses 1 and 2 can be found in the works of such writers of the past as Joseph Conrad, Mark Twain, and Charles Dickens, but it now ranks as perhaps the most offensive and inflammatory racial slur in English. Its use by and among blacks is not always intended or taken as offensive, but, except in sense 3, it is otherwise a word expressive of racial hatred and bigotry."
"Negro" has not been used in the U.S. since the early 1970s, when the National Conference on Black Power decreed that the use of the term "Negro" would be discontinued, and "Black" would be used in its place. (The term "African-American" later gained preference in the early 1990s.)
The word "nigger" is so inflammatory in the US that it is only referred to in the press and in news broadcasts as "the N word." African-Americans use it among themselves in varying degrees, and it is used in the lyrics of some rap songs, but (as MrP mentioned), not all Black people sanction the use of the word. Certainly, though, a non-Black person should never, ever use the N word.