Before I married I dated a few guys from my group of friends from university.
Your beliefs about smokers obviously do affect your reaction to them. Likewise, it's not impossible that your beliefs about black people affect your response to their appearance. Not impossible. But not inevitable either, so let's suppose your lack of attraction is innocent. The rest of your question is: why shouldn't you comment on people's appearances in just the way you'd comment on art? Why can't we proclaim the ugliness of some person or race? Simple answer: people aren't art. There are different rules for talking about people because the impact is different. If you are tempted to openly announce your dislikes, you might want to ask yourself why.