After we got rid of all the demeaning and derogatory phrases from the English dictionary, the time has come for the merely descriptive ones to follow suit.
Terms like "differently abled" are getting traction (I wonder, when did the term "disabled" become offensive?) and the reason must be to appease an audience that never ceases to be offended by even the most trivial utterings. Taken in its literal form, I take the specific phrase to connote a person that is equally capable of normal function, but by different means. To elaborate, with the end goal of a certain action remaining the same, the person uses different means according to his capacity of action of achieving said goal without the particular means hindering their ability to come to the desired outcome with the same ease as their equivalent. To give an example, if there is a glass of water on a countertop from which I want to drink, what I would do would be to raise and extend my hand, hold the glass and bring it to my mouth. To satisfy the condition mentioned above, for an individual to be characterized as differently abled, they should have to be able to achieve the same goal with approximately the same effort. The means by which they achieve it may differ, but the outcome should have to be the same and achieved with the same or similar amount of effort. Given that (following our example) our hands are the only mechanism of our body that can perform such function with the least amount of effort, any omission of such functionality would lead to a decrease in glass-handling capacity for the human body. Feet would be the runner-up for the task, but it would take an increased amount of effort and time to sustain a hold firm on the glass, let alone bring it to the mouth and drink. It logically follows, then, that a person with no hands would have no means by which to perform similar actions that can only (or extremely more easily) be performed by our upper limbs. The desired outcome could be achieved, but the means and effort expended would not justify the characterization of "differently abled" as a synonym of "equally abled". It appears rational, then, that the term disabled is not only appropriate in this case, but it is the only alternative available to us.
Although one could take it a step further and assert that a bodybuilder's body is more capable and efficient than a normal human's, our point of reference should stand somewhere in the middle: a fully functional human anatomy as defined by our current status in the evolutionary timeline. Deviations towards a leaner or stronger physique should be allowed without impeding the definition (i.e. a bodybuilder's and a thin person's hands can perform most trivial actions with equal ease).
Now to make an attempt on what a differently abled person might be, let's kick it up a notch and assume that somewhere a person is born without eyesight, but with the ability to construct an equally accurate version of their surroundings using the rest of their senses and the brain mechanisms to translate this into an identical image of their environment. We can think of this person as an equivalent of Marvel's Daredevil, but without the necessity for rain. Now, this person could register as disabled, since he lacks the ability to see in reference to the functionality of a fully functional human anatomy. The addition of the capacity to represent reality, though, as accurately as the rest by using different means (the rest of the senses as opposed to the eyes) necessarily renders that person "differently abled". The goal remains the same (to have a visual representation of the surroundings), but while the person does not possess the ability to directly see, he has other means by which he can assert the world around him with equivalent ease. The example might be far-fetched, but it clearly illustrates what different - in the sense of equivalent - means in this case.
Just because there are no cases like these in our world, words like "disabled" are a necessity to the language. Words do not inherently bear negative connotations; they merely reflect the sentiments and meaning assigned to them by people. When a statement contains the term "differently abled", my perception of the intrinsic meaning of its reference does not change; I assume that the subject has an impediment or the inability to perform an action, or reach a goal as a result thereof, that I can carry out with an ease that satisfies the definition of a fully functional human.
I also claim that our aversion to any phraseology that might cause offense is detrimental to the object as well. Teaching a child with reduced motor functions that she is as capable as her classmates creates a sense of false expectations. Maybe a child of an early age does not have the capacity to grasp the extent of the problem - and I can concede here that timing and approach is important - but totally eliminating and refusing the existence of an actual problem does not do any justice whatsoever to the situation. It goes without saying that we should be accepting of all people regardless of any difference in physical and mental capacity, but masking the problem is turning a blind eye to the situation. Maybe the actions taken to facilitate recovery and incorporation remain persistent regardless, but semantics matter and in this case serve as an explicit acknowledgement of an actual problem. I could never assume that "disabled" means "of less worth" as regards to human life and its importance, and the existence of people that would does not in any way justify any alteration to our language. The bottom line is that, whichever way we choose to express a situation, the underlying meaning remains the same. By a considerable stretch, it is the same case as saying "the 'F' word". You haven't uttered the word per se, but you put me in a position to replay it in my head where all I hear is "Fuck".
I do not in any way suggest that my views on the subject are correct. Issues of linguistics and semantics are always being revised in the background and what might seem unnatural now, might feel completely normal in thirty years as our discourse keeps evolving. For this reason, I cannot - and do not - want to assert any rigidity of my claims on the subject. I fully support any efforts towards inclusivity and justice, but it looks like these terms have been falsely substituted in an era of extreme political correctness and social justice; ideas of humble and honorable beginnings, but taken too far in the process.