The only thing I strongly disagree with is the urban myth that MRIs turn implants into projectiles. I don't think that can happen. None of the videos you linked show anything of the sort.
Yes, objects can be accelerated to dangerous velocities; but only if they can move freely (eg. oxygen bottles on a cart, wheelchairs, small objects placed on a smooth surface). Objects embedded in tissue can not move freely and won't start tearing holes in your body like reverse bullets.
It can of course still be dangerous. One lethal case documented in the literature involved a metallic clamp inside the patients head. The MRI seemed to have moved or dislodged it causing cranial haemorrhaging. It killed him, but it did not shoot out of his head like a bullet.