The best and fastest way is to start from the ground, with poles and then jumps so that he is given the opportunity to be independent.
Chances are he will rush the same way from the ground.
If he gets emotional while riding, do the same exercise at trot, if he's still emotional, walk towards the jump and stop in front of it and pet.
He has probably been punished at some point or another for refusing and this is the result. :)
Hi Gypsi! I have the same problem with one of my mare, small jumps and cavalettis have to become really random to him. You can jump a bar or small obstacle once or twice almost everytime you ride, at a random moment in your training session. He will progressively get used to it. You have to focus on not changing anything in your attitude, as if the fence did not exist (on small jumps if your horse is on a good balance, relaxed and well orientated the distances won't matter). Try to jump the bars while staying on a circle or curve, if you come straight and from far away he might anticipate. You can also get him used to going over the bats while trotting and not cantering. Stop him gently after the bar if he rushes and if you loose control, calm him down and try again. You won't have everything the first times you exercise him this way, be patient, with time he will identify the small jumps as a normal exercise of the training and will keep calm :)