I agree this page is problematic in present form and probably needs to be rewritten by Rob Bensinger. As it stands, I suppose, it's trying too hard to rescue the sort of person who does try to solve the whole problem in 15 seconds using one simple trick - a class which unfortunately includes a number of prestigious people whose brain goes into some kind of… mode.
I see a lot of force in your worry here, but I don't know what I can do about it myself, except maybe rewrite the page so that it pretends to only be addressing outright cranks. I've made a couple of edits to that end, and to remove some of the particular language you singled out as problematic.
If it were up to you, how would you handle the problem of the 15-Second-Solvers, possibly ones with high status? Just give up and accept that we shall always have them with us?
Separately: I do worry that act-based agency is overreaching in how much it claims to solve with how simple of an idea. But it's not like you're putting it in uncritiqueably vague or delayed form, and it's not like you came up with it in 15 seconds (so far as I know). Building a persistent edifice and defending it in detail is fine.
The current technical agenda isn't supposed to be a complete solution to 'building AGI without getting killed'. Why would it be? Did something give you that impression?
Separately: re: Arbital: As of June 2016, we're not currently focused on debate features (like the probability bars) and are just trying to make Arbital useful for conveying explanations. Explanation does seem to be a subset of debate features-wise, but it also means that Arbital's main use case is for explaining knowledge that's already there. Which is why the public face of Arbital is focusing on math where things are less controversial. In other words, all I can do is bow my head and say 'sorry' about the fact that at present, all we can do is have different people write different Arbital pages and try to courteously link opposing views where they've been written up.