1) Well, guess what? I didn't suggest it was! Nor does the discussion require universal truth!
Aramis said, "...the average dungeon crawler is a serial murder and robbery team event." (emphasis mine).
I responded saying that I think "most" published adventures provide a framing such that this isn't true.
Nothing here about universal truths. Only discussion of averages and overall leanings.
2) Yes. If you (generic, not Argyle King, specifically) want to make an assertion about non-published things that folks do at home, you really need to provide some support for how you came by information about what's going on in thousands of private games if you want to be taken seriously.
3) Heck, I partially addressed it in my first post in the thread.