Clear the migration history and let the community decide
A moderator can prevent the Q & A from being auto-deleted by clearing the migration history. This would make it appear as if the migration never happened; in other words, a regular question asked directly on this site in the first place.
The question would be unlocked but still closed, and no longer subject to automatic deletion by the system. Users could then vote (up, down, reopen, delete) as they wish.
This seems like a sensible option to me, because although the question is poor, the answer has value and might be worth saving.
The other aspect to this is that poor questions normally get a second chance, via edits and a reopen review. This second chance is denied to a rejected migration. Clearing the migration history would allow the more normal process to take place.
We'll see how the community reacts to this option.
After a week of being featured the voting suggests the community here would prefer that this Q & A were not auto-deleted. I have unlocked the question so it is no longer marked as 'migration rejected'. Clearing the migration history would have had a side-effect of reopening the question, which is a step further than I want to go by myself.
The question is now eligible for votes to reopen or delete.