Where is the argument for the conceptual slippery slope?

I do concur with the position laid down by Brendan Kelly ¹ in commentary on the paper by Verhofstadt et al ² and his conclusion that ‘we should not kill our patients’. However, one argument he has surprisingly not used is that of a ‘slippery slope’. In particular, Beauchamp & Childress ³ specify two versions of this argument. The psychological–sociological one is well-known and is often cited as an argument against euthanasia. However, the conceptual slippery slope is by far the more dangerous and is exemplified here so succinctly. In Verhofstadt et al we have ‘unbearable suffering’ as a concept leading almost effortlessly and uncritically to the euthanasia of psychiatric patients who have no terminal disease. What is so shocking is that this is no sterile philosophical debate: it is in action in a European country and has led to patient deaths. This subjugation demonstrates the biggest risk in the euthanasia debate and should be actively resisted.