The primary example that he might be referring to is this one [1]. It's someone reporting on their experience connecting to an ethernet port in his tesla and getting a call from Tesla to please stop.
To clarify, they disabled it for everyone in a software update[1]. Some comments made it appear they just disabled it for this guy due to his hacking, but it was for everyone.
He could have disconnected the car from the internet before he started fiddling around if he wanted to hide his activities. The car makes no secret of the fact that it's always connected.