he has nothing to suggest that such a lack of evidence indicates anything.
That’s a different discussion. As you said,
The whole point of this discussion is that his reasoning does not coincide with his actions.
I was simply arguing that your characterization of his argument as inherently self-contradictory was incorrect. Yeah, his supposed priors are probably wrong, but that’s a different issue.
But what is the date? Is it 2 months? 6 months? A year? 5 years?
Okay, say it’s 6 months. Does that make his argument non-contradictory?
If I predict it’s going to rain soon because of a long dry spell, when it rains that doesn’t prove me wrong.
Doesn’t his position make sense if he believes that:
if there’s no organized fifth column, we should see some intermittent, disorganized sabotage, and
if there is an organized fifth column, we should see NO sabotage before some date, at which there is a devastating attack
?
Of course, I agree that it’s likely he would have made a different argument if he had seen evidence of sabotage—but as presented it seems his position is at least potentially coherent.