Let me rephrase this another way:
Let's say you're at a bar with some friends, one of whom brings along a new guy. Everyone is having a good time. At some point, the bar's resident ice queen walks in. Everyone in your group has tried to pick her up and failed, using every approach in the book. New guys says "I'm going to try [insert line/approach that everyone has already tried]." When the guys say "Dude, you have no shot if you try that, every regular in this bar has been shot down pulling that out," they aren't being haters. And when the guy goes over there, if he thinks that they're not validating his approach, it's likely that he doesn't believe in it either. So he has no confidence and gets shot down.