And, importantly, the process of providing that proof must be open to the notion that it is not safe to fly. It is possible (and IMO very likely) that this aircraft is fundamentally unsound, by design, and that no amount of tweaks and fixes can change that. They made a dangerous aircraft, bullshitted their way through the approval process for commercial travel, and now must pay the price.
"Fundamentally unsound" seems like a subjective judgement in an area that clearly requires numbers.
Wikipedia tells me there are 1445 of these planes in the air each flying, what, 3000 miles a day on average? The existing accident statistics would argue strongly that this plane is "safe" in an absolute context, even if it's clearly "more dangerous" than other models. The big reason people are so upset about this is that it's a safety outlier in an industry that has been extremely safe, and getting inexorably more so, over the last half century.
Don't forget the MCAS fiasco, as well.
Or the engine deicing you can’t leave on for more than 5 minutes because it might start a fire.
That's the point.
The problem isn't specific, it's systemic.
But the 737 MAX Process/Program is known to be defective. I'll take possibly bad over surely bad any day.
┌──────────────────┬──────────────────┐
│ Bad Design │ Bad Design │
│ │ │
│ Good Process │ Bad Process │
├──────────────────┼──────────────────┤
│ Good Design │ Good Design │
│ │ │
│ Good Process │ Bad Process │
└──────────────────┴──────────────────┘