Alright, I think firstly, it's important to listen carefully where the guy commenting is coming from:
1) if it is a "novelty/popularity" thing (think 'your favorite sports team lost and the other guy is not supporting your team') then I would make a joke like "who would have guessed that the car doesn't fix itself if you hit it with a massive piece of metal" - and then move on to other amazing features of the car/different topic. Keep in mind: people like to gloat and people like to "push your buttons". So if you get defensive / start the whole explanation/discussion as soon as you are given the keyword, people might bring-up the topic, just to see your reaction. So relax, take a deep breath and laugh it off.
2) if it is a "safety" thing ("don't put the kids into this fire-trap") then I would start addressing the story with all kinds of safety stats. Watch out: these things tend to get emotional. So don't get lost in stats and numbers but explain it graphically and do comparisons on what else is dangerous etc.
Roughly I would follow these chain of arguments:
1) Everything is dangerous. The question is, what tradeoffs we are willing to make
2) The car itself was fine. It got into trouble due to an OUTSIDE impact - i.e. this won't go up in flames spontaneously (it's not a Dreamliner kind of incident)
3) After it got damaged the car warned its driver to pull over: Which other vehicle does that?
4) After it finally caught fire, the passenger compartment was kept in tact (and as an aside, the fire was contained etc.)
5) If all this doesn't work, start the process of "how should the car have behaved?" and then go through the different ways cars should ideally react to accidents