This is ridiculous reasoning. Do you think every new food product that hits the market is tested for years beforehand to make sure it doesn't kill anybody? Soylent is just food, not some new medicine.
Soylent is being sold as something that you can eat for every meal. You can argue that most people aren't going to do that, but that's how Soylent are selling it.
Soylent claim, unambiguously, that it is safe for everyone. People with Crohn's disease sometimes need to eat a liquid feed. Is Soylent safe for them? Because Soylent claim that it is safe for them, and that it'll provide them with optimum nutrition and bring them to good health.
I agree with you that they should not be selling it in that way.
But I'm trying to be more a "critical friend" rather than just "negative". I realise that I don't yet have the right balance.