To be fair to the journalist, she might think that ATH are a reputable source, given that the government have invited them to give evidence to them, and they've also advised the NHS.
But - this is how hokey organisations like that build credibility. Every time an organisation or other entity with credibility publicly associates themselves with ATH, then it's another thing that'll come up in a quick google search. If a journalist - or the BMJ - can't be bothered to actually check out ATH's credentials, but instead googles them and assumes that other people have done due diligence at some point, an organisation like ATH can make itself appear credible when it's anything but.
The BMJ publishing this, also adds to this undeserved veneer of respectability.
But we expect more from the BMJ (and the government, come to think of it!)