It's weird to me how many things I find flagrantly dangerous, "experts" find acceptable and vice-versa. Whether it be design, or policy.
That being said, there are certain institutions and experts that I've found are more trustworthy than others (The Electronic Frontier Foundation for example) so I do usually trust them over the opinions of others. Basically there is a lot of nuance, never blindly trust anything.
Regarding the topic of the Tesla door handles, I've always felt uneasy regarding the safety of them.
You can always find washed up academics, ex-industry, ex-government, etc people who will reliably show up to say stuff in return for money. Lawyers do it too.
No. Ibelieve lots of things experts believe, often because they believe them, in fields where I have no expertise.