The only time I use the term "behaviorist" is when referring to a veterinarian with a specialization in behavior --
American College of Veterinary BehavioristsWhat is a veterinary behaviorist?Or to someone who is certified by the
Animal Behavior SocietyApplied animal behaviorists are scientists, educators, or other animal professionals with an advanced academic background in the principles of animal behavior. Applied animal behaviorists may have a background in fields as diverse as psychology, biology, zoology, veterinary medicine, or animal sciences. They may work in laboratories, zoos, farms, animal shelters, universities, corporations, or as private consultants (and beyond!). What applied animal behaviorists have in common is the application of scientific principles to improving the care, management and welfare of animals in captivity and the wild.
Unless the person meets the qualifications for one of those, IMHO they're just a trainer. But there's no regulation on who can call themselves a behaviorist, so . . . buyer beware.