I've met some (OK, most) who were quacks. They claimed to cure diabetes, measles, etc., by spinal manulipation.
I've also mea a few who only claimed to be a sort of masseur. One told me his entire course was two years of anatomy but he didn't claim to do more than relieve stress. Most of his clients were long-haul truckers and football players.
They were at least partially honest. The truly honorable thing for them to do, having realized that Chiropractic, as a science-based medical treatment, is a fraud, would be to chuck their Chiropractic Diplomas in the dumpster along with the rest of the worthless diplomas from places like Hamilton University, and go get a certificate in physical therapy.
But to call themselves "doctors" is to add insult to injury.