I think there's a way to be like Simon but without being rude. Just give direct and honest feedback. What's wrong with transparency?
It must take a lot of work to prepare an insightful honest answer. A shady answer gets the entrepeneur out the door without the need for putting together a well-structured argument.
VC's almost unanimously claim that they like what they do because they get to be involved in helping entrepreneurs succeed. I don't doubt that to be true. They could be more helpful with a bit of effort put into providing true, honest feedback to entrepreneurs.