The argument isn't “Daily Harvest's product caused gallstones”, it's “Daily Harvest's product caused liver damage with symptoms strongly resembling gallstones, and as a result plaintiffs received irreversible surgery with a risk of life-long side effects”.
There are several questions here, and the legal system is the right place to unpick them. From the top of my head:
- did DH's lentils cause liver injury?
- is that injury permanent or temporary?
- were gallstones misdiagnosed because of the injury inflicted by DH's lentils?
- was unnecessary surgery performed due to misdiagnosis?
- did the doctors misdiagnosing gallstones/performing unnecessary surgery meet the standard of care?
- did the unnecessary surgery cause permanent/temporary harm?
- was the direct harm (temporary liver injury) caused by DH's lentils reasonably foreseeable?
- was the indirect harm (surgery, surgical complications, lifelong side effects) caused by DH's lentils reasonably foreseeable?
A lawsuit is the right way to get answers to these and determine who, if any is liable for damages and in what amount.