The worst thing you can do with a scared horse is make them go toward the scary thing. Even in a gentle way. To the horse, a "little positive encouragement" is A TON of pressure when they are scared. To the horse, that thing is dangerous, even if we know it's not.....but horses and humans don't think alike, so it's our job to put ourselves in their place and to understand why they are afraid and to do what it takes to make them confident.
For a snotty attitude "No" the worst thing you can do is try to MAKE them do it. You will just end up with a fight on your hands, and you won't win, plus it does nothing for the relationship. No horse can respect someone who MAKES him do anything, you have to get the horse to WANT TO.....that's the key.