Saying "Sure, people shouldn't care how pretty your UI is." mischaracterizes user interface design as being about prettiness rather than interaction. But that might in fact be your very point and you might actually talking about the mischaracterization of others.
I was thinking of the fact that beautiful software is perceived as more usable, all else being equal (http://www.ergonomicsclass.com/wp-content/uploads/2011/11/Tr...). This is irrational but not controllable. Unfortunately many good solutions lose out in the market because their developers make the mistake of expecting users to be rational econs, rather than accepting reality and working around it.
Saying "Sure, people shouldn't care how pretty your UI is." mischaracterizes user interface design as being about prettiness rather than interaction. But that might in fact be your very point and you might actually talking about the mischaracterization of others.