Words mean things.
If I cry out, at the top of my lungs, that "Pizza is fucking bullshit!", then go on to say that I hate how pizza kills people, tears countries apart, and delivers atrocities, people will narrow their eyes and say "Actually, I think you're thinking of war." And then they're going to be a little weirded out that I said something so simultaneously bizarre and incorrect just to get their attention.
The thing is, when someone says "design is a differentiator," they're not really talking about how it looks, either. Because appearance is very rarely a lasting means of differentiation.
My criticism is not that he's using the word wrong. It's that he's invested a lot of flaming in the process of misunderstanding people who aren't.