If the cult of the amateur is growing, it's a direct response to the failures of said professions. As budgets are repeatedly slashed (we can't afford to actually audit those accounts!) authority dissolves and ethics collapse. The grassroots pro-am revolution didn't create these problems, its filling a vacuum.
The writer of that paragraph had previously maligned lawyers, accountants, teachers, doctors, journalists and others. Dennis' point (if I can paraphrase) is that it's a pretty sad day for the professions if these things can be said to be true, but in fact they're not true.
His defence is based on the premise that it's not technical knowledge that defines a professional - it's how we use it that matters. And I agree with that. I think being a professional requires technical mastery of a subject as a prerequisite, but not as a characteristic of the status. It is the application of that knowledge that counts. When it comes to application the requirement is to profess, that is to state an opinion that is honestly formed based upon the available evidence that answers the question that is posed. Most importantly though, that answer must be objective in the sense that it does not just answer the question in the way that the enquirer might wish to hear. It must do so in the way that the professional thinks is right.
This is what professional ethics are about. They require the exercise of independent judgement in the pursuit of what is seen to be in the interest of broader society. That's why I've said before now that an accountant has a duty to others before their duty to the client standing in front of them. It's the fact that this has been forgotten that has given the 'amateurs' the chance to eclipse the professionals. The person who claims to be professional but who does in fact merely seek to serve the interest of the piper who calls their tune is not a professional at all. They're propagandists. And unsurprisingly no one takes heed of them. Nor should they.
It's getting over this issue that will challenge the profession. So, and for example, when we see the tax professions making measured contribution to tax debate rather then delivering the standard knee-jerk reactions that all tax and everything HMRC does is a bad thing that remains almost universal on their part we'll have some idea that they can be trusted to be using their judgement as their status requires. Until then they remain destined for the margins because people will not trust their judgments. And rightly so.