Is Haku a man or a woman? In Naruto, Haku is a rogue Ninja that fights along Zabuza. He has a sad history of death and mistreatment that I won't treat here.

In any case, the Haku's peculiarity is that although he looks/behaves/dresses like a woman, he is a man. But not all sources agree with this, so... Is Haku a man or a woman? 

Is there a reason for the first part in my spoiler? Or is it just a plot device?

If your answer contains something that appears or is explained after the Bridge battle with Team 7 (as far as Haku is concerned), please use a spoiler.
I do not think that Haku was considered as a woman is considered a spoiler. 

After all, they discover that only 1 episode after Team 7 met him. I can guarantee for sure that Haku is a man. Despite what other sources probably say, there are plenty of men in real life who look like women (Justin Bieber is good example). What I cannot tell you is what was the perspective of Zabuza for him (if he was just a Friend or something "Else").

I say this only because the one who told Naruto that significant detail was Haku himself, so there isn't a lot of room for mistakes.