Originally Posted by touchofsleep
I set up some cones and asked him for a canter. He almost looks scared and just started bucking like a wild bronco.
I'm pretty positive that's what happened. Exactly same thing happened to me once years ago when my horse suddenly saw those scary cows running towards her at the team penning. Even though she had seen them before. VERY scared --> bucking. I was unprepared so landed on my back.
My suggestion would be to introduce new things slowly. If he's scared - don't canter, but rather walk/trot first till he's comfortable.
BTW, we can talk for hours about "disrespect", "bad training", "horse shouldn't be bucking", etc. but it is what it is. You are done with it, analyze why it happened, and work on it so it wouldn't repeat itself.