Actually, "defensible driving" does exist as a term, but it means exactly what you think it should: driving that can be defended in a court of law or public opinion.
- Ability to operate a motor vehicle and observe legal and defensible driving practices... (from a bus driving training site)
- Among the Australian women, safe and morally defensible driving was more closely linked to the blood alcohol limit enforced in Australia... (paper on drunk driving in Australia)
- Operate a vehicle, observing legal and defensible driving practices... (job requirement)
- Representation in court by an attorney for defensible driving tickets...
There are ~ 275 hits on Google. Most of the others were either mistakes, repetition of a joke, or separated by a comma.
Your argument is quite defensible.
DEFENSIBLE DRIVING: A young man had just parked his car in his office building's garage when he noticed a friend pulling in. As the young man approached his friend's car, he noticed that her windshield was busted and that the car's bumper was covered with blood, leaves and twigs. Concerned, he asked, "What happened?"
"I was in an accident ... I ran over an attorney," she said.
"Well, that explains the broken windshield and blood on the grill, but what's with the twigs and leaves?"
"I had to chase him all through the park!"