It's interesting isn't it.
Saying you don't date someone because of age, ageism!
Saying you don't want to date certain races or say certain races better looking, racism!
Saying oh I won't date guys below 6ft? heightism?
oh I won't date guys/girls who aren't hot. looksism?
I guess the difference is, with beauty being subjective, if you would date a black women if you met one that you found attractive, that is not racism.
Refusing to entertain the idea as you believe they are all unattractive even if you haven't seen them all, that is racism.
Obviously if you refuse to date any specific race because of preconceived notions ("all dirty", "all thieves", etc) then you are a full blown bigot my hypthetical friend.