I think many are finding it quite difficult to understand how someone could allow an animal in their care to be transported in a trailer with a rotting floor, to then allow that animal to suffer for 3 weeks before being euthanized, and then blame everyone but yourself. Granted those who transported the horse bear much of the responsibility, but so does the owner who allowed the horse to be put in a substandard trailer.
As for this not being abuse, I don't know what else to call it. In most states, if you drive a child without a proper restraint you can be ticketed for neglect and endangerment, if that child is then injured or killed as a result of that negligence that is abuse. Why would it be abuse if you cause a child to be injured but not abuse in the gross negligence shown this horse?