YABU
That’s like saying legal abortions shouldn’t exist at all, because it could be expanded beyond the current gestational limits to full-term for any reason at all. That could theoretically happen, but despite being in place for many years, it hasn’t- because there is not wider acceptance that it is necessary or right. Of course it is possible that if medically assisted dying was brought in for those with terminal illness that it could be expanded to include other groups- but it is far from inevitable. Not every country with assisted dying includes under 18’s, those with mental health problems (and you can be suicidal and still have capacity, incidentally), or those with disabilities. If you never changed any laws or practices because doing so had not gone the way you would hope somewhere else, nothing would ever change or progress. We need to look at what has gone well and what has gone awry in other places, and use that to inform how we do things to mitigate or avoid those problems.
Assisted dying does not have to expand beyond terminal illness, it hasn’t in every country where it exists. I’m not exactly sure that disability should always be excluded- lots of safeguards needed, obviously, and I could see the argument for not allowing it but I have personal experience of someone who became disabled and who did not wish to continue as they were and ended their life by assisted dying- I can see it was the right decision for them, having had that conversation. They were not depressed or mentally ill- and actually very well supported through rehab, had all the adaptations and equipment etc. All the physical support needed, close family and friends, very loving and supportive partner and absolutely no financial worries- yet they did not want to live this life with the restrictions they had. Not done on a whim, long time spent trying to come to terms with it, therapy, all sorts- to no avail. I’m glad they had the option they took, though sad they had to leave family in order to do it.
It’s not being suggested in order to finish off all the frail elderly patients or anyone with a disability - and no single Dr is going to be able to decide “right, I think it’s time you were dead” and kill them- so the fears the NHS will start killing off the elderly right, left and centre on a single Dr’s whim is just nonsense.