That was, incidentally, sekasi's point #3, several parent references up:
"3. Always respond to requests for more information"
"3. Within reason, always respond to requests for more information."
Many communication "rules" require the ability to moderate one's interpretation of the rule. I don't think this is any different. It's a good thing to give candidates feedback and if they're confused, the feedback did no good so you should be willing to help them understand. But if they're just unwilling to see the world or themselves for what they are, it's out of your hands and you should leave it well enough alone.