I love this. Yes, "First, do no harm." That's precisely what I do, hoping that my students will grow with deepening trust in me and in one another. That way, as comments grow more incisive, they know implicitly and explicitly that they are intended for good. But that takes time and patience and a checking of the ego. No one is "right" when it comes to critique. But a constructive, candid, well-intentioned conversation can help the writer find their way.