Earlier this year, I watched the behavior of the horses in my herd as they watched the farm slaughter process of some other animals (not horses). They were curious, they watched, they were not scared by the rifle shots, they were not upset as the carcasses were hoisted, skinned and cut up, they mostly just wanted to know if they could have some of the leftover hay in the pen where it happened.
The guy is a jerk, no doubt about it. If he had a cause, it certainly hurt more than helped. I have read that the video was shot over a year ago and has just recently surfaced because AR people decided to use it at this time.