These people do harm in at least 5 ways: they profit from bogus therapies; they shrink the pot of money available for health care; they harm people directly by their sometimes dangerous procedures; they promote magical, pseudoscience thinking; they scare sick people away from effective therapies.

In terms of action at some point letters/pressure on government can be effective. My belief however is that they rely on counting letters, as opposed reading them and evaluating the quality of the arguments and evidence contained.

It is difficult to know the best way for this harm to be addressed.
My guess is that we should probably try to generate some public interest and outrage about what is being foisted on them by chiropractic corporations. Only then might there be some significant number of people opposed to them.

We might try to organize some effort locally among those who are dissatified with chiropractic services perhaps acting with the Federal Health Fraud agency http://www.bureaudelaconcurrence.gc.ca/eic/site/cb-bc.nsf/eng/h_00020.html.