I wouldn't be persuaded to "let the AI out" by that argument. In fact, even after reading about the AI box experiments I still can't imagine any argument that would convince me to let the AI out.

For some time now I suspect that the argument that convinced Carl Shulman and others was along the lines of acausal trade. See here, here and here. Subsequently I suspect that those who didn't let the AI out of the box either didn't understand the implications, haven't had enough trust into the foundations and actuality of acausal trade, or were more like General Thud.