Is it okay to call the reader's target audience stupid?
I'm a tech genre author, and have already published one book on Android development. However, this book was focused more on the developer of the apps, than the user.
Now I'm working on my second book, which is on app UI. In this book, there is a lot of focus on the usability of the apps, making it as easy as possible for the end user to accomplish the task.
Among developers, you can frequently find statements in casual chats saying stuff like
users are stupid,
if your software is idiot proof, a better idiot will be its user etc, all basically saying that users do not think the way we do, and what might be blindingly obvious to us, is not so obvious to them.
I'm asking if it's acceptable to say things like the following in a proper printed book:
Users are stupid/dumb/something. You need to position your UI elements in such a way that it is impossible to miss, and make its function so clear that even the dumbest user cannot fail to understand it.