You appear not to have read the part of my comment where I explained that Mystery Method is heavily about quickly befriending groups of strangers and getting them on your side.
Ok, yes, that does sound like a generally useful skill, and I was not aware that some of the things you cite were part of PUA material.
But none of that is what was originally cited by the OP. What was cited was the drink-buying thing, something which just sounds positively wacky to anyone not committed to the PUA ethos.
If he'd cited an example of something like what you're talking about here, I don't think anyone would have had a problem with it.
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: