it seems that there is some phenomenon wherein some mentally ill people (hard to see how this person was "sane" by any measure) find ISIS-type Islamism very attractive. An interesting topic and thinking about it rationally (as rationally as possible?) may lead to new insights, but what will those insights be? I don't think it is immediately obvious.

There can be no doubt that there are some Muslims who have declared war on the United States and some of those Muslims are in the US (likely very few..though the qualification "very few" may not apply equally to the UK), but what to do in response is still an open question.

Given the current state of Western civilization, it may be necessary to discuss "counter-value targeting" much more before it is implemented. For example, the targeting of cities and sacred symbols of the Nazis or the Japanese occurred in the context of total war and clearly defined enemy states..and in a setting where the culture broadly accepted that A. We are at war B. Our enemies are evil and ruthless and have attacked us first. C. This is what one does when fighting evil enemies who are equally determined to do this if they had the chance (and in fact have already done so at places). All three elements are currently disputed at home; This may be a bad thing, but it is a thing. It may have to change before such targeting makes sense...and, more to the point, before it works (instead of splitting apart the home front or the allies, for example).

Just a thought.

PS: what is disputed is not the fact of an attack on the US. After 9-11, obviously US has been attacked.... But by whom? Bin Laden and his group were not a state. If the cities and symbols of a state have to be attacked in response, then which state? (Afghanistan was already attacked for harboring him, Pakistan was spared for various reasons, Saudi Arabia as a state was not really harboring or supporting his network...and of course, Iraq or Syria had nothing to do with that particular attack). Mecca (for example) is a central symbol for many who had nothing to do with him, or actively opposed him. If the government of Saudi Arabia is fully on board with attacking Bin Laden (and it probably was), is it OK to attack Saudi cities? ..and so on.
Suppose ISIS manages an attack on the US. Would it be OK to carpet bomb cities under their control? Mosul? Raqqa? Much less bomb Mecca (whose controlling state is actually bombing ISIS?).. (I bring up bombing Mecca because I think slapout may have mentioned that as an option at some point. My apologies if my memory is faulty)
Leaving aside any moral objections, wouldnt it be desirable to spell these options out in advance, to make such deterrence work? (if it works at all). Could the US and its allies really spell such things out in their current incarnation?
I think the US is capable (as in able and willing) of bombing cities right now, but not capable of saying it out loud and clear before or after the fact, which makes it rather less effective as a threat, no?
They really didnt have to spell it out in 1944, likely because times were different?
Thinking out loud.