More specifically, he targeted chiropractors' claims that their services could help children with asthma or colic, and of course they were making a fortune off these claims. Responding like the scientific professionals they are, the chiropractic community sued this man for libel and took him to court.
Most anywhere in the civilized world, you're within your rights to criticize a profession as long as you don't wave your penis at people while doing it. When the courts began to investigate Singh and found that his accusers didn't really have any sort of a case, they turned their attention back to the chiropractors.
"Oh yeah, this'll cure the shit out of your AIDS."
What began as the opinion of one man soon became the interest of the British government, as it began to discover that a lot of chiropractors were indeed not helping anyone but themselves. As a result, about 1 in 4 chiropractors in the UK are now under investigation by regulators for making bullshit claims.
As for the unfortunate Mr. Singh, he had to pay over 200,000 pounds ($311,000) in court fees, almost lost his job, and has been relentlessly badgered by the chiropractic community. But in the end, he did win his court case, and as a final dick-punch to the chiropractors, the judge ended the ordeal by stating that what was originally Singh's opinion should now be considered fact in light of the new evidence uncovered.