This is going to be pretty quick as I expect what I'm about to say has been said before by people much better at it that myself but here is my take.
Firstly Simon did say something a bit dumb.
You might think that modern chiropractors restrict themselves to treating back problems, but in fact they still possess some quite wacky ideas. The fundamentalists argue that they can cure anything. And even the more moderate chiropractors have ideas above their station. The British Chiropractic Association claims that their members can help treat children with colic, sleeping and feeding problems, frequent ear infections, asthma and prolonged crying, even though there is not a jot of evidence. This organisation is the respectable face of the chiropractic profession and yet it happily promotes bogus treatments.
That is not a statement to win friends. Equally though it doesn't deserve to be labeled libel. The piece is clearly comment/opinion to begin with and within the realms of comment/opinion the claim that there "is not a jot of evidence" should be reasonably permissible - the argument should be clearly that within the author's opinion there is no reputable evidence that supports the BCA's claims.
This isn't how the court has seen it.
In fact the court didn't even hear the case as the judge read a pre-written judgment as soon as the parties had said their piece.
This judgment was impressive in taking the case far beyond what was expected (even I expect by the BCA) in that by using the word "bogus" Simon supposedly meant that BCA made its claims with fore-knowledge that they were harmful (some of them are but I don't think many chiropractors believe this). That the BCA practices maliciously is clearly far more than Simon meant through the use of the word "bogus" (in fact I've never known it to have the connotation that something was maliciously false just false).
This case is terrible on two fronts - firstly it highlights some of the problems with libel rules, secondly it shows just how important good scientific reporting is and how hard it is to produce.
In terms of libel like a lot of the grayer areas of law its a very difficult thing to balance - too much on the side of the plaintiff and it becomes to write anything without either filling it with 'apparently's and 'maybe's or being sued. Too far the other way and you can say what you want with impunity.
Whats interesting about this in terms of the law though is it highlights the problem of online blogging. If Simon had initially published his piece as a blog would the reaction have been the same? whats going to happen when blogs start getting picked up and published by papers? Will it be libel in the country posted from? from the country its hosted? In the US blogs are protected speech and cannot be sued for libel. As more of our journalism is done from the net these sorts of problems will arise.
Moving on from the legal aspects (which I can only question as my law knowledge is pretty poor) the journalism aspect is even more interesting. This sort of case is a huge problem for scientific reporting. The bottom line is that this case represents a large group suing someone for being critical of their methods.
Scientifically Simon is reasonably well supported - there isn't much good evidence that chiropractic treats much other than bad backs. Saying that shouldn't get you sued. Even in a national paper - if there is a genuine scientific basis for a statement saying so shouldn't land you in trouble.
If we're being fair so long as you set it as opinion you should be allowed to say pretty much what you want. It doesn't work but it might encourage people to be a little more critical in their assessment of claims made by people. Libel laws are their to protect people from unfounded claims - unfortunately a lot of organisations know how to avoid them and a lot of individuals don't.