He named the product based on the Soylent from the book Make Room! Make Room!, which was a Soya / Lentil product meant to feed the masses, but the movie version Soylent Green had turned that into a mix consisting of human parts. While I understand he references the original book, the majority of folks familiar with Soylent from the movie context associate it with the human-composed product. This is what makes it unfortunate and unintentional -- I don't think they wanted / intended this association. And that's what marketing is -- it's creating a market perception and demand for a product.

It would be as if someone came up with a new, super-high end car and called it a Yugo. No matter what you do, you could never completely erase the pre-existing market perception even though the new product might be totally different.

He can't possibly have been unaware of the fact that the movie is far better known than the book. Even if he meant it as a reference to the book, he must have been aware of the movie.