Stanford's Jay Bhattacharya helps explain the Great Barrington, MA, "Declaration," in a November JAMA livestream with Harvard's Marc Lipsitch. There are a lot of nuances in Jay's arguments that are omitted or only vaguely implicit in the GB declaration.
But the biggest challenge I see in taking GB seriously is that its calls to protect (only) the vulnerable almost seem practically disingenuous. Lipsitch doesn't make this point exactly, but reducing community spread is clearly the second-best but practical solution. I wish Jay had offered a clearer assessment of the various marginal costs of these mitigation strategies.
Given the findings in JAMA Network Open by Ogedegbe et al., it has further become more questionable whether there really are vulnerable people outside of nursing homes, or whether instead racial and ethnic minority groups have been hit so hard by COVID19 because they must work and must live in closer proximity to one another. The costs associated with protecting them alone would surely approach the costs of "lockdowns" that reduce all activity, although it is also conceivable that the benefits of doing so would also be larger.