I had an odd over emotional reaction recently too, and I understand that feeling of being upset that it can still make you mad.
I know too that feeling of not wanting to go off at JW's because I can remember being on the other side of the fence and being completely genuine about it even though I was wrong.
Still, you made some excellent points! I wish I could be that fluent at the drop of a hat. Im sure if hes a thinking person he will think about what you have said, and if he isnt a thinking person you wont have done any harm to his ego or his world view. In fact you will have done him a favour by persecuting him for being in the 'true' religion!