It can be both, security researchers don't get a free pass just because they are exposing a wrong.

Had someone died you might (in countries which have it) get corporate manslaughter on a company that ignored security warnings. You absolutely would on the researchers and the journalist for their reckless disregard for the lives of others.

Yes, researchers don't get a free pass. Nothing is free. They've risked lives and their reputations to save lives. It had happened before in the history. And hopefully it will happen again. Some times it is worth it.

(*) without risking lives there wouldn't have been a video documenting these life-threatening vulnerabilities in the cars.

Rubbish - there would be a video of them on a test track. Much like all the videos proving quite how fast the cars can go. You don't drive a McLaren F1 at 240mph on the Interstate and post it to Wired expecting to get away with it...

They did not only risk their own lives. They put other people around them at an increase risk when it was unnecessary. That is the argument, that it was not necessary. This same demonstration could have been done on a track or other controlled environment where the public was not in danger.