The employer in this instance should be under an obligation to protect his/her staff by providing lifts/methodology for performing the tasks.Well, if you're in a line of work that requires you to sometimes manage heavy objects ... whether they be people or inanimate objects ... then there are techniques and mechanical aids that should be made available to you to do so without hurting yourself. I've already described a couple of these techniques that you should have learned on your way to becoming a DM, and there are others that your employer should make available to you if it's their decision to provide services for this type of clientele. That's a business decision. Your "right" is to decide whether or not to be in this line of work, or to work for this particular employer. If you decide to accept the position, then it's your responsibility to provide the services that are paid for by the client your employer agreed to provide services for. You don't have the "right" to discriminate against certain types of clientele simply because you believe they should not be there. Nor do you have the "right" to insist on government intervention preventing those people from being provided those services. That's called discrimination, regardless of how you look at it.
Furthermore ... if you're the sort who thinks about your clients in terms of being an a**h**te simply because you don't like the way they look, then you're in the wrong line of work. Perhaps you'd be happier in the fashion industry.
What makes you better or somehow more deserving of this "right" you mention than an EMT or nurse who has to deal with heavy people on a daily basis? I can assure you those people put more time, effort and expense into getting into their line of work than you did as a divemaster ...
... Bob (Grateful Diver)
With the EMT/ nurses, they should generally have access to lifts/PAT slides and training on lift techniques (definitely the case here).