Full Idea
It is argued that the mass murders of the Nazi period had their small beginnings in the Nazi euthanasia programme.
Gist of Idea
The Nazi mass murders seem to have originated in their euthanasia programme
Source
Jonathan Glover (Causing Death and Saving Lives [1977], §14.2)
Book Reference
Glover,Jonathan: 'Causing Death and Saving Lives' [Penguin 1982], p.186
A Reaction
This is the 'slippery slope' problem, and it seems undeniable that killing gets easier as you do more of it (e.g. on a farm). But not all slopes are slippery, if the focus is retained on reasons and justifications.