Ooops, shouldn't have posted before reading the whole thing. Still, my arguement stands; what defines the "goodness" or "badness" of universe being destroyed and immediately replaced with another identical to it in all the most miniscule ways (the memories of agents interacting with the time machine), or for that matter the "betterness" of the previous universe.

Technically, this means "time travel" is less accurate that "history re-writer", but to me, that doesn't sound any worse.