When people say they are attracted to a certain race, they are then called racist. The implication of calling them racist is that they must submit themselves to those who they aren't not attracted to, in my opinion.
Most Helpful Girl
It's a term used by people who can't get beautiful white girls or guys like Paul walker.1
Most Helpful Guy
A preference is only racist when the person choose not to date a person from another race due to seeing them as either inferior or if it's based on racist belief, such as everyone within that race fits a negative stereotype.
If a person simply does not find people of a particular race physically/sexually attractive, then that's not racist, since we can't help what turns us on. However it does tell us that, that person has been indoctrinated since birth on what is beautiful and what is not.
People call others racist for such preference because to be honest it sounds racist. Unless the person goes in detail and explain why exactly they won't date someone from another race, then the phrase "I don't date X people" will always be interpreted as a racist attack.0