The magnitude of physical stress waves a magnet has to undergo to be demagnetized is huge. Most magnetic materials will shatter instead unless the force is applied precisely.

I think he vaguely remembered something about electromagnetism and that water on electronics is a no-no.

The main takeaway is that he should appoint an engineer to advise him on technical topics (and Surgeon General on medical matters, etc.), otherwise any sufficiently sly corporate sponsor or media can easily steer his policy by pretending to be experts. I guess the only fields he does not need to delegate are being a douchebag on TV and lying about real estate.