Why do I have a desire to call any old man, a "future dead man?"

I know they're future dead men because they're GUARANTEED to be dead in the future.

I'm a future immortal because I'm young enough to reap the benefits of advancing medical science long enough to become clinically immortal once the ways to make clinical immortality reality are discovered.

If anyone is younger than retirement age, they're potentially future immortals too.

Future dead people are too old to live long enough to reap the benefits of clinical immortality because a medical breakthrough to make them clinically immortal will not come along in time to benefit them. That's why they're "Future Dead People."

Now if you were an old person and I called you a future dead man / lady to your face, how would you react?

And why do I have this temptation to call old people that?