Don't want to sound arrogant, but it seems that projects like this was a good lesson for you. With one lesson (among many others), that "I carefully explained all my suggestions and backed them up with UI conventions..." will not work with some people (technical ones) and there should be other styles of communication in your toolbox. I learned this the hard way when I wanted to be a freelancer and had to do everything (coding, managing project, accounting) on my own. Now I work at a company as a coder and project managers are "shielding" me from clients eccentric needs.