It is hard to tell whether anyone took this seriously - but it seems that an isomorphic argument 'proves' that computer programs will crash - since "almost any" computer program crashes. The “AGI Apocalypse Argument” as stated thus appears to be rather silly.
I don't see why this makes the argument seem silly. It seems to me that the isomorphic argument is correct, and that computer programs do crash.
Some computer programs crash - just as some possible superintelligences would kill alll humans.
However, the behavior of a computer program chosen at random tells you very little about how an actual real-world computer program will behave - since computer programs are typically produced by selection processes performed by intelligent agents.
The "for almost any goals" argument is bunk.
From Geoff Anders of Leverage Research:
Not a surprising result, perhaps, but the details of how Geoff taught AGI danger and the reactions of his students are quite interesting.