he should have broached this with the companies in the first instance and they did not take any action then go political with it.
Companies would have simply ignored him. What are you expecting from so careless people that design flawed products that endanger their customer's lives
just to cut costs? They only care about bad PR, which is what exposing everything to the world does.
What you mean for "going political"?
Personally making it publicly known that this is possible is irresponsible if not downright immoral and unethical.
Not saying it and hoping an actual homicidal hacker does not find out the same stuff is more immoral (There are brilliant minds even in the criminal underworld).
By exposing the faults they will patch them within months/years, and everyone will know that this is a danger and plan accordingly.
By not exposing them he allows others to kill people. Which is also criminal offense for most nations.