Are chiropractors quacks?
Yes. The entire system is based on nonsense, and has never been scientifically proven. It's just as credible as homeopathy, which is also a scam.
Incidentally, I have never encountered a chiro who was pro-vaccine. In my experience they are invariably opposed to vaccination, and other forms of science based medicine. You can virtually guarantee that they'll end up trying to push some other kind of woo to boost the profits of their practice.