It is the logical progression when we stop valuing all human life as sacred.
No it isn't. It is pretty much the definition of the slippery slope fallacy. There is no suggestion or evidence at all that allowing assisted suicide leads to killing weak babies or killing handicapped people without their consent.
I also struggle to see how forcing someone to live on in incredible pain is treating life as sacred. Why are you so tied up in quantity of life rather than quality of life?