It is simply accurate that there is a large group of people, well represented on this site, who consider autistic-oriented, non-PC discussion of dating rituals to be "beyond the pale", and to be universally condemned in the strongest terms, a reaction nearly indistinguishable from their position on terrorism.
I don't think that you are trying very hard to understand their actual views. Even if they used the phrase "beyond the pale" (which your use of quotation marks implies), it is not valid to assume that all actions deemed "beyond the pale" are considered to be morally equivalent. An act can be considered "unacceptable" in a certain context, while still being vastly preferable to some other act.
You say that they want to condemn PUA discussion in the "strongest terms". Even if they used that phrase (which you don't imply because you didn't use quotation marks), do you really think that they meant that literally? Do you really think that your evidence justifies the claim that they reserve no stronger terms for terrorists?
Suppose that Omega presented one of the people whom you're thinking of with the following choice: Either a PUA discussion will happen on LW or a terrorist attack will happen somewhere. Do you really believe that this person would be indifferent between these choices?
Your conversations with such people certainly justify the belief that they take a very dim view of PUA discussions. But how could you justify a strong belief (you call it "simply accurate") that they would be indifferent between the choices above? Have you engaged them in equally extensive conversations about their views on terrorism? If not, how can you be so sure that they don't consider it to be even worse?
I think that you could justify your inference only if you had good evidence that they considered PUA discussions to be so bad that literally nothing could be worse. I don't think that I would believe someone even if they explicitly said that they felt this way. I would assume that they were either engaged in hyperbole, or that they just hadn't paused to reflect on just how bad things could be. The only way that I could be convinced that they were accurately representing their views is if we had wide-ranging conversations about all sorts of very bad things, and they steadfastly maintained, with all evident seriousness, that they would not prefer that a PUA discussion happen over these things.
But perhaps your sense of the phrase "moral equivalence" does not imply that they'd be indifferent between "morally equivalent" acts. If so, what do you mean when you say that someone considers two acts to be "morally equivalent"?
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: