> When would it have been alright for the FBI to release the update? If they waited until after the election, the other side would accuse them of covering it up—appropriately so.

The FBI's and Justice Department's long-standing rules on the issue are: 1) Never discuss ongoing investigations; and 2) take great care to never say anything that will at all affect an election.

So while your question is an interesting one, the FBI has two clear, long-standing answers and rules, and they violated them.