If you're going to take my 2-year-old car and stick half a tank of diesel in it, you can at least help conduct an experiment to see if my thinking as to the appropriate solution is right. Turns out it was. Common sense at the time would have been to drain the tank (after cursing them out for being so negligent). I figured that common sense is often wrong, and that the gasoline pickup, which floats in the tank, so why not just fill it up with gas and drive?
It beats having to properly dispose of half a tank of diesel contaminated with the gas that was left at the bottom of the tank, and it's cheaper. Plus, I was not getting out of bed at 2 am to deal with this.