Earlier quoted context omitted.
Cars weigh thousands of pounds and routinely drive upwards of 60 miles per hour. The success of the first iPhone or Facebook app didn't depend on using it to navigate through life-and-death situations not only for the users but also for everyone around them. There are places for 'move fast and break things'. But cars move fast already, and they can really break things.
Tesla’s infotainment and IT infrastructure is unrelated to their safety. If this guy worked on motor control or braking system firmware then that would be scary, but he didn’t.
2. Apparently people can ssh into the infotainment system.
1 + 2 => someone hacks into the infotainment system and flashes a safety-critical ECU. I guess/hope there's some protection in place to prevent that.