but I've got some hangups about our ability to make objective decisions about what is "in something/one's best interests."

Yeah, me too :/ It's like every human (or animal) right - it has to be enforced by people, and people are pretty shitty. I don't think that means we reject the principle, it means we put guardrails around it to try and prevent errors and abuses.

And I certainly agree: lab grown meat is far less heinous and morally offensive than factory farming. It involves a moral compromise for vegans, but, well, so does almost everything else. We can recognize both aspects.