Question: The issue has crept up on me slowly over the last several years. I am increasingly aware of the massive debt that many of my students are taking on, debt which is far beyond the sort of debt that I incurred as an undergraduate in the 1980s. Because of this, in recent semesters I have found it somewhat difficult to fail students. Instead of simply asking myself "does this student deserve to fail this class?", I find myself asking "does this student deserve to have their life ruined?" In many cases (e.g. students who are already on academic probation) this is not much of an exaggeration. It is a very bad situation to find yourself in your early 20s with no college degree but $30,000 in debt. In some cases, I am aware that a decision of mine might be a contributing cause of a student ending up in just such a situation. I can no longer regard a failing grade as a relatively minor matter (like a speeding ticket).

How do professors reconcile their de jure role as guardians of academic integrity with their de facto role of being (at least in part) responsible for their students' economic future?

Answer: 
Take the example of a medical student. Do you want to pass someone who does not have the necessary knowledge to treat patients correctly? It is your duty to make sure that only the ones who know what they are doing will pass. This may be less strict in other subjects but the principle is the same.

--- EDIT ---
Another example where this becomes clear would be an airplane engineer or pilot that does not have the necessary knowledge (thanks to Mike's comment below!).
All things in life can cause you economic ruin these days. House mortgages, car loans, hacking, frauds. 

It is basically a society based on debt-based servitude where the banks are our overlords. You are likely just one well-meaning person in this huge mess and likely cannot affect this fact. As far as I know you also can not affect what these students future employers will base their decisions on. 

It is not your moral obligation (nor is it even within your power) to try and steer where these students end up. It is the privilege of these debt overlords to do.

Your job is to teach and to grade. Do your job, peasant.