If somebody needs to pay for their insulin with a credit card, chances are they're already not very well off.

So, start with a baseline mediocre life due to financial constraints. Oh wait, you're also diabetic. So let's drop that quality of life further. Now you're $800 in debt, plus interest. Chances are you're not paying the balance off next month, and if you're not paying off the balance then you're probably using credit to pay for your next batch. Now you're in a cycle of paying off your debt, similar to payday loans. Your "disposable" income is now shrinking each month. You sacrifice meals, and you don't do anything enjoyable because most things cost money, but you need your medicine to live. Eventually you end up so deep in the hole that you either have to sell what you have (i.e your home, if you even own one), or claim bankruptcy - which as a low income earner will limit your potential to pick yourself up even further. But wait! You still need to buy your insulin, and now nobody will lend to you. Now you've lost the value you've built throughout your life AND the debt keeps piling up.

Death sure sounds like an enticing option now. What's the point of living if it's in misery? You very well may rather be homeless for the rest of your life (while still being diabetic but not being able to afford your medicine), but I'd rather die.

You're missing the point. Yes, of course if you have the cash or credit you will buy your insulan rather than dieing. Some people don't have it and will try to do without and some of them will die. The fact is, morally, it shouldn't be an issue at all.