The reviewers of NIH grant applications are charged with helping the Program staff of the relevant Institute or Center of the NIH decide on relative merits of applications as they, the Program staff, consider which ones to select for funding.
They are not charged with trying to help the PI improve his or her grantspersonship*. They are not charged with helping the PI get this particular grant funded on revision. They are not charged with being kind or nice to the PI. They are not charged with saving someone's career.
They are not charged with deciding what grants to fund!
If they can also be kind, help the PI improve her grant for next time, help her improve her grantsmithing in general and/or in passing save someone's career, hey great. Bonus. Perfectly acceptable outcome of the process.
But if the desire to accomplish any of these things compromise the assessment of merit** in a way that serves the needs of the Program staff**, that reviewer is screwing up.
*Maybe start a blog if this is your compulsion? I've heard that works for some people who have such urges.
**"merit" in this context is not necessarily what any given reviewer happens to think it is a priori, either. For example, there could be a highly targeted funding opportunity with stated goals that a given reviewer doesn't really agree with. IMV, that reviewer is screwing up if she substitutes her goals for the goals expressed by the I or C in the funding opportunity announcement.