A New Twist on Learning From History

From what Jackson Diehl has written, it appears that the new lessons of history are:

1. Unless the current event is exactly like the historical event, there's nothing to be learned from history.
2. If somebody has drawn a historic analogy that proves flawed, it conclusively proves that any comparison of the current event to the history event is flawed.
3. If somebody claims that a particular lesson is to be learned from a specific historic event, and you disagree, you can reject the idea that anything can be learned from the historic event.
4. Absent a perfect analogy, anybody who analogizes a current event to a historic event is being unhelpful.

Diehl is offended at the notion that the war in Afghanistan can be compared to the war in Vietnam, arguing "No military mission since Vietnam has come close to that war in the number of casualties, or in its consequences for the United States". Those are the only two measures that are relevant? And when Diehl suggests that the consequences of the war in Afghanistan are significantly less for the United States than the consequences of the Vietnam War, is he making an argument for withdrawal?