"A remark generally hurts in proportion to its truth," suggests that honest or truthful comments can be more painful than false ones. The idea is that people are more sensitive to remarks that reveal uncomfortable truths about themselves or a situation.
This quote from James Patterson's book Invisible highlights the idea that honesty, while valuable, can also cause emotional pain because it exposes reality, which might be difficult to accept. The impact of such remarks depends on how closely they reflect the truth of someone's feelings or circumstances.