Preamble: The Problem with Slippery Slopes
The reason many oppose medically-assisted dying is the fear of going down the "slippery slope" resulting in horrific abuses. Therefore it's critically important to understand the real role of slippery slope reasoning.
Slippery Slope Reasoning is Just Bad Logic.
Slippery slope reasoning is to provide arguments against a particular action based on the assumption that the action, once taken, will inevitably open the door to similar but increasingly less desirable actions until finally terribly immoral things are being allowed.1
People like the Nazis in WWII have gone down slippery slopes to horrific abuse in the past, so many point to history as a legitimate basis for this concern. However, to simply assume that such a slide is inevitable or that the future must be the same as the past is to engage in bad logic.
Legislative Protections are in Place
There are many legislative options to stop the slide down the slippery slope--to draw the metaphorical line in the sand and say "no further". A great example of this is Oregon's Death with Dignity Act, which has so many safeguards that it is impossible for anyone who does not meet their rigid criteria to participate in the program. Other legislation in the Netherlands prohibits healthy seniors from being euthanized except when strict criteria are met. In both cases, we stop the slide long before abuse becomes an issue and the legislation that stops the slide includes serious penalties for going further.
Every law and regulation has potential loopholes, but that doesn't mean we shelve the laws because we're more afraid of future problems. Instead we enact necessary laws then find and close any loopholes, making the law a better fit with real-life application.
Slippery Slope Fears are Not Supported by Evidence
The burden of proof that the slide down the slippery slope is inevitable, probable, or highly likely rather than just possible is on the person making the slippery slope argument. Imagine someone saying "I'm afraid if I have kids my child would be an X, so I just won't have kids at all"--this is the fallacy of the slippery slope in action and no reasonable person would accept such a claim. Without the supporting evidence the slippery slope is simply not a compelling justification to avoid otherwise worthwhile behaviour.
Slippery slope reasoning is the result of fear combined with flaws of logic and misunderstanding of the facts. When faced with such claims lacking justification, our response should be to point out that such a slide is not, in fact, inevitable and to identify and explain the associated legislation that will stop the slide.
Remember that the burden of proof is always on the person making the slippery slope claim, so until that proof is given and logically examined for accuracy we are completely justified in rejecting such claims.
1Johnna Fisher. Biomedical Ethics: A Canadian Focus (2009 Oxford University Press. p. 139.)