>What I would definitely NOT do is pull out my rolodex and "contact every colleague I have client-side and agency-side" (this must be hundreds if not thousands of people)

meh. In almost certain likelihood the guy didn't do that. It would make him look childish to his contacts and would waste a bunch of his time. Why do all that work when he can get the same effects (scaring the guy and telling him to fuck off) just writing a tweet?

Much more effective. Though it does tell me never to do business with Campbell.