There is nothing cruel about hobbling a horse. This has been done for centuries and is used by many nomadic horse peoples. The OP did not "hobble" the horse but rather tied on leg up to the barrel of the horse with rope and then asked the horse to move around the round pen.
I will say that I woud not use the word "abuser" with this person. Abuse to me is made with aforethought to be cruel, and the OP did this out of ignorance and being guided by some trainer who espoused this method, ala the "Horse Whisperer" fame. The result might have caused pain to the horse and a risk of injury and I personally would probably never do this, move from fear of injury than causeing pain. We do all kinds of things that cause pain to horses, though usually only for a second or two.
The Op has admitted a bit of ignorance in this area and actually has been pretty willing to listen to the comments of most posters here.
YOu WILL get a better result from treating an animal OR a person with respect than you will with harsh blows or words.