Thanks for the correction, Rich. I have never been accused of being logical.
I agree with your point. I don't agree that Graham was asking for nastyness when he put his stuff on the net. I do agree that he will get it. But David would not be quite logical saying that Graham caused David's action. Right?
No he didn't cause David's post, but we are not discussing cause and effect.
By posting a viewpoint online we are inviting others to read, consider, accept, reject, comment, etc.
Simply because we do not agree with the response does not make it wrong for the person to provide it.
Nastiness is also somewhat subjective and I don't agree that this was/is nastiness; it was phrased frankly without dressing it up, possibly a touch of frustration or exasperation (I can't really speak for David so I'm guessing here...).