Give us ALL his background. Have you seen a trainer /instructor to help you? Have you ruled out veterinary problems? Have you had his teeth done and re-checked? IF say he has raced, then already proceeded to be passed around, hasn't got any vet or teeth problems and you HAVEN"T seen an experienced horse worker - then yes - I would say he would be a candidate for being put to sleep, otherwise, see to all the above first. I agree yep there are plenty of other good horses out there but that doesn't mean that this horse doesn't deserve to have his behaviour investigated. He very much *might* be one of those good horses that is trying and has been trying to tell his owner for a while that something is not right and she may not have been 'listening' very well.