Hi. Is the word 'man' used exclusively for humans, or it can be used also for extraterrestrial small humanoid green beings, with developed brain? I remember from start trek, that Klingons were somewhat offended by the fact that humans call Klingon females and males women and men.
Well, we've never met any aliens and we don't even know for sure whether they exist, so we haven't had an opportunity to put this to the test.
Star Trek, of course, is fiction. Whether an alien race would actually object to such terms if we ever made contact with a real one is not something we can possibly know. But I think that if they were similar to us, we might instinctively call them "men" and "women"; if they were very different from us, perhaps not.
Of course, if we met friendly intelligent aliens, and some of them came to live on earth, we might have to think of alternatives to phrases like "human rights". After battling with racism and sexism, we'd have a new problem on the horizon: specism.
Of course, anyone who is British will have heard of Doctor Who, a very popular science fiction/fantasy TV series. The protagonist is an alien time traveller -- the last of the ancient race of the Time Lords -- known only as "the Doctor". He looks just like an ordinary human, but he is 900 years old and has two hearts.
In the episode The Christmas Invasion, he refers to himself as a man. He has just regenerated -- a process whereby a dying Time Lord undergoes a transformation, getting a completely new body and a new personality to go with it (which explains how the franchise has managed to continue since 1963). Having just recovered, he faces an enemy but is also exploring his new personality -- what kind of a person is he? Later on, he says, "Now I know what kind of a man I am: I'm lucky." And a bit later, after he kills his enemy in a very inventive way, he says, "No second chances. That's the kind of man I am."
As for his enemies and non-human friends, it depends. The Slitheen family, from a race of ugly, green creatures, disguise themselves as humans, but they maintain their gender -- the female Blon (and a female Slitheen can shoot poison darts from her finger, which male Slitheen can't) disguises herself as a female human. Accordingly, the Slitheen are referred to as "he" and "she". The Daleks, though, are little squid-like mutants living inside small, tank-like travel units; they don't seem to be male and female, and are referred to as "it". None of these creatures are referred to as "men" or "women", though.