The difference here is that this is a complex moral and legal issue to which we as a society have not yet reached any sort of consensus (and if anything, the historical consensus lies against Scott Adams' view).
I tend to be extremely nervous about the idea of legalising euthanasia; especially in, although not limited to, situations where the patient is unable to voice an opinion on the matter. While there might be occasions (and perhaps Mr Adams' situation was just so) where death is 100% certain, recovery is impossible, and suffering immeasurable, in which case the case might be more clear cut. But as soon as you legalise the possibility of legally killing someone, you open the door to all sorts of injustice. What if the person has dementia, and the family "persuades" them to agree to euthanasia because "they're such a burden, and they're not even themselves anymore"- even though the person is actually still emotionally happy in their reduced state? What about people with seriousness illnesses (like cancer) who get depressed and demand euthanasia- even though there is a possibility of curing the disease and every likelihood that the depression would pass eventually? It is a terrifying minefield.
So, that said, if anyone advocates euthanasia I'd like the chance to debate with them, to get across my views and my worries and try to get them to see beyond the immediate and the obvious (and give them a chance to allay my fears). However the tone of Scott Adam's rhetoric would make it impossible for me to engage with him on the issue. It's aggressive and amounts to bullying on an extremely serious issue. How the hell am I supposed to engage someone in discussion, on a matter which I'm not even 100% confident of my own opinions, if the response I'm going to get is "you're an evil torturing bastard and I wish you death and misery"?
I'd be willing to excuse it for heat-of-the-moment grief-stricken talk. But if he really thinks that way and is prone to repeating the sentiments into the future, then he loses a lot of respect from me.