Racism in Science Fiction

I recently read a discussion about the racist ways minorities are portrayed in Science fiction and this lead me to think about the nature of writing and how different groups are portrayed.

I am not, but my family are little people (people with dwarfism etc.), Why isn't there more attention to the problems of how little people are treated in fiction? They are always portrayed as freaks in sci fi. I really think the issue should be on honoring our unique differences and celebrating the things that make each person unique. What is racist is to group people solely on skin color, height, culture, language etc. A good story has all of the elements that make up the setting you have created. If you bring in a character that doesn't belong and is not part of the story just to have a certain race, then it is tokenism. The answer is simple, be realistic. If you are a white writer, can you genuinely write about an Alien perspective but not the black perspective? We all share the human perspective which should include all humans all races and all heights.