Matt Perman in (his excellent book) What's Best Next describes the Christian ethic that demands user-friendly websites:
"We are to care about usability because hard to use products make life harder for people, not easier. And the Christian ethic is to lift people's burdens - make their lives better - rather than create burdens for them by making their lives harder in order to save ourselves some time and efforts in the design of our products. This means caring about usability on your website, because usable websites not only will get you better results but also will serve your customers more effectively."
He goes on to share some other implications for this ethic:
"It means that if you are in marketing, you need to create your marketing initiatives in a way that doesn't annoy people or seek to use them but instead will serve them even in the way you market to them."