Terry Bisson's "They're Made Out of Meat" (flash fiction, science fiction, humor, free): Reason these aliens won't contact humans
In this much milder & humorous variant of Arthur Clarke's "Crusade", an alien survey ship has chosen to simply not make a record of humanity's existence because they find the idea of meat-based intelligence disgusting!
Rusty has saved me trouble of writing anymore; his post on it is detailed enough.
Fact sheet.First published: Omni, April 1991.
Download full text.
Nebula Award 1991 nominee in short story category.