I use plastic lawn chairs and PVC pipe when jumping my dog (hes in agility, I only have a few regulation agility obstacles), and from my experience with that, I wouldnt put a horse over them unless you put the pole on the very top over the back, but that would obviously make the jump much larger than what you have pictured. I also clearly remember fooling around with my friends jumping the same obstacle. I got a bit clumsy and grabbed the pole with my ankle. The entire thing came with me, and pulled me to the ground. I can't imagine if a horse had a similar incident. I wasnt badly hurt, maybe a bruise, but if a horse had fallen like that?
Should you have your horse taken away? God no. He/she looks very happy and healthy in your care. Whoever said that was being rude or jealous. I would uust advise againat thisparticular jump