No, that's rude and a huge generalization.

But really. Media thrives on perpetuating stereotypes. It doesn't have to be acceptable, because people will go see movies DESPITE blatant bigotry if there's enough explosions/sex appeal/fan service/whatever. Meanwhile, people who believe in the stereotypes can justify themselves and people who behave according to stereotypes feel validated in their behavior.

Cracked actually just presented an article about sexist stereotypes. One of the stereotypes they talked about was PMS and they brought up this same point. The stereotype of "Crazy women with PMS" allows women to brush of their retarded behavior as "Oh I'm just PMSy, not a total bitch", and it allows men to either brush off women's bitchiness (or justified anger at something he did) as PMS, or justify a sexist belief that women are unfit for X-task because of emotional instability.

ANYWAY. I guess the reason Hollywood does it is because Hollywood CAN do it. And people have become comfortable with these stereotypes, so they do it to keep the audience comfortable or just because its the easy way and they can get away with it.