Benjamin Clayborne
Auror
Would remaining alive by machine, with no hope of ever becoming conscious be living a life or would that be simply existing? Would turning off life support be cruelty or would it be humane?
If someone's brain has been damaged to the point where the information comprising their personality and memories are lost (e.g. not even hypothetical super-advanced medical technology could restore them), then they literally are just a bag of meat, and the person you knew is already lost forever. In that case, yeah, I'd pull the plug as quickly as possible just to get it over with.
If the person's just in a coma from which they might theoretically awake, then no. As long as there's still a chance, I wouldn't do it. (Unless they had a DNR order for that exact situation, in which case you have to respect their wishes.) I mean, I like to think I'd do what they wanted, but you can't really know unless it happens.