Users aren't being fooled here. People learn that progress bars aren't accurate, and things like the author mentioned, "when it gets to 75% it will really be done".
First, no, as the other comments here attest, the end result of constant lying is that nobody trusts progress bars at all; if things reliably finished at 75%, progress bars would be easy, but they don't so they aren't. Second, that people soon get used to being lied to does not make lying OK.
To me, JeremyBanks' second sentence clearly implied that users don;'t trust progress bars anymore, and your comment was unnecessary. He is also certainly implying that lying is not OK. Interpreting them otherwise seems like a strange kind of contortion to me.