@ Jamie Japanese are the most polite people to me. Ms. Miki and Ms. Chihiro are native Japanese and they are teachers too. They explain the use of " 男" , if it stands by itself is rude, it is their opinions, and it is not rude in expressing their opinions. The fact that was given: "when I referred to one of the customers standing outside as 前にいる男. They told me that I should say something like 前にいる男の人" Here, the Japanese was physically insulting you, misusing the Japanese Language. Since you did not ask for his/her help, criticising your Japanese in the public is rude. The issue that you raised which telling us that the Japanese are so critical of their own language. They are so rude to those non--native Japanese speakers. Ms. chihiro_ito is my favorite pal at Italki. Please don't mislead us to the wrong side that all Japanese are rude.

I kind of got the impression that 男 is like an adjective and pertains to anything masculine (usually not standing on its own), and 男の人 is specifically a man or men. As you probably already know, adding (の)人 behind a word/character makes it a person who can be described by the character before it, like 男の人 is man (person of masculinity), 女の人 (person of femininity), 日本人 is a Japanese person (person of Japan), etc. Just my thoughts on it.

I think the meaning is the same, but there is the difference. 男の人 is a polite phrase and women usually say it.

@wozitoya I said that what Miki and Chihiro_ito said is RIGHT. I am supporting them. I am not saying that they are rude. I don't say that Japanese are rude anywhere. Please read my comment again.

What Miki and Chihiro_ito said is right. Listen to them and don't give them thumbs down, they are native Japanese speakers lol. When I used to work in a Japanese restaurant the staff thought it was funny when I referred to one of the customers standing outside as　前にいる男. They told me that I should say something like 前にいる男の人 or similar because just saying 男 sounded harsh/rude.