Turns out his book How to Tell a Story and Others does mention this, sort of, but it goes like so:
But the teller of the comic story does not slur the nub; he shouts it at you--every time. And when he prints it, in England, France, Germany, and Italy, he italicizes it, puts some whooping exclamation-points after it, and somtimes explains it in a parenthesis. All of which is very depressing, and makes one want to renounce joking and lead a better life.Now, that's out of context, but you get the idea. I think this is what John Grogan was referring to, but I'm not sure it's a commentary on exclamation points in general, more that he didn't like their use in triplicate in a specific, and sometimes general, instance. What I found more interesting (like the italics?) was how joking was somehow causing one to defer any attempt to "lead a better life."
Of course, maybe I just didn't find what Grogan was referring to and I'm just rambling. Suck it up, it's my blog and I can ramble if I want!!!