The sale has already been made by the person who bought it originally.
My moral justification is based on owning the media. If I don't own the media I'm downloading, I feel morally disgusted.
If I own the media and have sourced it though legal means say retailer, second hand store. What is the difference between downloading or ripping the medium?
Downloading saves me the hassle. However, I won't download a blu-ray version if I only own a DVD version. It has to be like for like.