You're missing the main thrust of the argument, I think (and this is maybe a little expected because the article kind of presupposes it).

Imagine a hippie concept such as "you are effectively the same being as that guy over there, if either of you gets hurt, it's isomorphic, it's equally bad to the overall organism".

Now, imagine that this is objectively true, i.e. there is something in the basic laws of reality that, if you could observe it, would show the hippie idea to be obviously true.

Then perceiving this part of the laws of reality would be anti-fitness, so you would evolve to be blind to it.