I don’t think this argument works. “I have a preference for someone to travel back in time and retgone me” is perfectly coherent. It is, as far as we know, not physically possible, but why should that matter? People have preferences for lots of things that they can’t possibly achieve. Immortality is a classic.
I responded:
I don’t think “time” is fundamental to the Universe. but let’s say it is. by some “meta-time” you will (in the future) go in the past. you still have existed before you went back in time.
Seth Nicholson wrote as a comment on Facebook:
I responded: