Nope, it's not. Sorry to all those political correct people out there, but this is just another case of "let's use words we don't really understand".
Racism describes a philosophy (and I guess here's where the first among you frown), after which a certain race is superior (or inferior, depending on your perspective) based on the fact they belong to that race.
That's it. If you say "all black people are thieves" then that's racist, since you imply a direct connection between being a criminal (a term usually connected with negative attributes) and their race. Same for the other side of the spectrum by saying "Only white men are fit to lead a company." (here you declare a set of positive attribute exclusively to white men, therefore denying those qualities to all other ethnicities and gender...s).
"I find all black people unattractive" however is - in and of itself- not racist. It's a preference of yours, a matter of taste. It might OFFEND people, sure. It's uncomfortable to hear someone say that you could never be attractive to him/her, no matter how hard you try. But unless you go on proclaiming that race's general inferiority, ineptitude or claiming that i.e. "one simply cannot be attracted to these people" you're not in the dreaded "racist"-territory.
Won't stop people from calling you that though.
Funny little detail at the end: If you'd consider the refusal to date a certain ethnicity (based on your personal taste) as racist, then following this logic, that would pretty much make every human who's NOT bisexual sexist.
So yeah, guess the message of the day is "Know your buzzwords."