I take full blame for allowing Ax to use it.
I've used a shock-collar in the past, and didn't see it being a big problem. However, you are right: I've let him walk over me as far as usage. It worked great for me in the past in extreme situations (when he ran after cars), but never actively used it outside of that.
We'll get rid of the collar, immediately. NILIF; I'll take a look at that.