The point is that whether and how much one wants to die tends to fluctuate a lot, and the willingness to commit suicide depends a lot on the availiability of means to easily and painlessly do so. A large percentage of suicide attempts are opportunistic rather than planned. The planned ones probably succeed more often, but that does not necessarily mean that those people really wanted to die more - just that their will to die was over a certain threshold for a certain time.
Criminal justice only if you tune out the rehabilitation aspect. Civil justice only if you tune out everything except punitive damages (which don't exist in many jurisdictions).
Read the (long) linked-to article from which the quote stems. Basically the point is that using violence to achieve a goal teaches the people involved that violence is an effective, legitimate way to achieve goals - and at some later point they will invariably have conflicting goals.
Presumably they also wanted a canal and there may well be an optimum point where you maximize some sort of combined utility
Jobs programs, even those that create nothing particularly useful, are about giving people a sense of worth and accomplishment, otherwise you could just hand out money. Obviously futile make-work activities like the one suggested achieve the opposite of that and are, indeed, often deliberately used to punish and humiliate people.
The point is that whether and how much one wants to die tends to fluctuate a lot, and the willingness to commit suicide depends a lot on the availiability of means to easily and painlessly do so. A large percentage of suicide attempts are opportunistic rather than planned. The planned ones probably succeed more often, but that does not necessarily mean that those people really wanted to die more - just that their will to die was over a certain threshold for a certain time.