@polarisera You're suggesting reverse burden of proof.
And also ignoring the possibility of the person in question being fully conscious and capable of communicating their wishes.
However, I was consciously staying away from making a point about the practical issues involved with assisted dying - on those I'm solidly undecided- and was merely adressing the bad argument of "we can't accept people killing themselves under any circumstances, because that would violate sanctity of life or something". And how that logic leads to banning things like DNRs and advanced life directives, if fully applied. At the very least it leads to having to not observe them if there's a chance the medical crisis is a result of a suicide attempt.