We do have brain analyzing machines. These are called reflexes. They do not depend on whether one is awake, sleeping, ill or well. When the brain is functioning “alive” these reflexes are intact. Loss of the reflex reveals no brain function.
In addition there are multiple scans that can be done that prove no blood flow to the crucial areas of the brain, EEGs that can show lack of electrical activity in the brain, etc.
It seems you do not want to hear the truth, just hold to your own opinion. As is famously said, you have the right to be wrong.
Forget about him — he wallows in his or her own ignorance. Much better suited for him or her to be at DU, where how you feel must be the fact.