Dont understand(reducing what),and up in arms?
Hey, for all you women making "ha ha now we won't need men anymore" jokes, just think about that statement turned around. (You're reducing a man to what he offers you sexually. If a man did that to a woman, everybody would be up in arms.)

Question

Answer

Reduce = become smaller. If you reduce a man, he becomes less important. Similar to a physical object.

Up in arms means many angry people, protesting or revolting.

Answer

Hi Hazem,

Reducing is in regards to men or a man.
A man is a complex being with emotions and feelings. When you say that joke, you are reducing that man to only what he can do in terms of sex. 
When someone is up in arms it means that they are protesting angrily, or are very angry about something.

I hope this helps. 
Aleks