You are absolutely correct, Apple does NOT have the right to dictate how the industry designs their phones. And in reality, they don't need to. They produce their designs, and the then the rest of the industry copies their design language. Maybe they use iPhone 5C colors on an iPad clone or perhaps use the chamfer from the iPhone 5 and the glass back from the iPhone 4 in a new model, it's still following Apple design.
As someone else mentioned, this happens in other industries as well. Like BMW's Bangle butt, that was then copied by everyone else (even though most BMW enthusiasts thought it was hideous).
Looks like Xiaomi is following Samsung's example (who followed Microsoft's example and then expanded it) by now moving on to copying other items (air cleaner in their case while Samsung copied Dyson's vacuum cleaner designs).