I could argue that there are cases where you could crash a plane in careful and not reckless manner. That is with extreme control, planning and probably minimising the potential damages such as environmental by removing as much hazardous stuff as possible. Plus having extensive planning on operation. Still unlikely to get approved, but I see it to be possible.

I am suggesting that it may be possible to safely, carefully, and legally crash a plane in a controlled scenario.

For instance: https://youtu.be/zuynxwQMad4

I think he's suggesting that the FAA regulation he violated was operating the plane in a careless or reckless manner. He did that by intentionally crashing his plane.