Black Women are Bitchy

I’m a college student and I’m currently taking a class that basically consists of learning about other cultures and discussing ideas we hold about these cultures.
My teacher asked several people the following questions last class:
1) Who are better drivers, men or women?
2) Who is bitchier, black women or white women?
3) Who is smarter, men or women?
Every single man asked said men were better drivers. Of the women asked, about half laughed and also said men were better drivers. The only woman who was unapologetically vocal about being a good female driver was a lesbian. One man claimed women just don’t have the attention span to drive and that they’re always doing their make-up or texting. When even the teacher claimed men were better drivers, I asked her why it is then that young men have the priciest insurance? She said it was because they’re very aggressive on the road (that doesn’t sound like good driving to me).
When asked who was bitchier of black and white women, I was the only person who argued against black women being bitchier (even the teacher said black women were bitchier). One white woman said “Black women ARE bitchier! I know, I wait on them all day.” Later someone said, “I think it’s just women in general.”
When asked who was more intelligent, every single man said men were, all but one woman said women were.
I just don’t get it. Why does one sex have to be smarter? Why does one race have to be meaner? Why do people cling so tightly to stereotypes?