The fact that chiropractors are the ones who have always objected makes the need for inclusion of such wording quite necessary. We can't leave it hanging for readers to just guess. The sources (and history) also make this clear. Other professions, like Physical Therapists and MDs, have recognized the danger and made patient consent mandatory. Only chiropractors have been in denial. (Why we still refuse to include the largest studies, such as Di Fabio's, which clearly show the great preponderance of chiropractic involvement in injuries and deaths, is beyond me. Regardless of that fact, I, as a PT, have always urged caution by all professions, and I stopped using cervical manipulation entirely, since other methods are more effective, safer, and longer lasting.) 

 As far as Herzog goes, I'm not sure that he's a "proponent", but he was hired to defend the profession from lawsuits filed by patients and their surviving families. Until he and his lab were figuratively and literally "bought" by the Canadian chiropractic profession, he did objective work. Then he started doing agenda-driven (pseudoscience) work for them and their lawyers. I communicated with him before his involvement, and later was saddened to see such a change of a fine researcher when this happened. Doing biomechanical studies on a cadaver for this purpose, especially when actual, incontrovertible, cases with living and formerly living (until their "adjustment" killed them) patients showed that it is definitely possible to cause strokes in living people?? No, the opposition to admitting any possibility of actual causation is pretty much exclusively limited to chiropractors for obvious reasons. Their stance is exactly the same type of stance originally adopted by the tobacco industry, and for the same reasons: "Deny, deny, deny. Never admit." Any non-chiros who might doubt the causal connection are the exception which proves the rule. Whatever the case, our sources mention chiropractors, and we should mention them. A straight quote should do the job.