Corporate rights are basically limited to the rights that any collective group of people would have, so self-incrimination doesn't make sense, but it doesn't get around the broader point that the same corporate personhood that allows corporations to be sued for copyright infringement, allows them to use the same defenses that groups of individuals (ie, co-authors) could use for copyright infringement. Could you sue "Alice and Bob" for copyright infringement because they watched a lot of movies before writing their screenplay? Nobody writes a screenplay from first principles. They're all based on all the other movies they've seen to some extent.