We see this bit of misguided but highly annoying nonsense surface every now and then. It appears to flow from the idea that by observing that someone does not have the same physical abilities as we expect to find in the default, that we are somehow diminishing or demeaning the person.

I class this with the fallacy of those who cannot distinguish between criticism of an idea or argument and criticism of the individual making the argument. As you observe, it is incredibly patronizing and annoying.