Psuedoscience occurs when people use scientific language to assert moral truths rather than to help organize thoughts about moral truths.  It happens as well outside of economics, but there are fewer opportunities to do so compared to what economics offers.  For example, it is not uncommon among biologists to assert that observable evidence regarding evolution means there is no God.  That, however, is pseudoscience in the same way that occurs with economics.  Lack of naturally observable evidence for God depends entirely upon moral abstractions and assumptions about what "God" means, but that does not stop people from making such straw-man assumptions and then arguing the lack of evidence for them. A similar thing occurs in economics with moral assumptions about justice and a good society and the kinds of evidence or lack thereof to support or refute claims about such abstractions.

This is further complicated by the fact that science itself has been given in current discourse a moral superiority that it shouldn't have.  If you can say something mathematically -- the language of science -- it provides credibility in discourse today that it really shouldn't have if the discourse were more about truth than about politics -- about who get what, and how.  The fact that economics uses the language of science to organize thinking about precisely the question of who gets what and how, makes it much more easy to abuse for discursive strategy rather than for truth telling than can be done with natural sciences.