"What I'm trying to say, in my long-winded, old fogey way, is that distinctions can be very important. Some radio people call any slow song a "ballad," which demonstrates their ignorance so plainly that it ought to embarrass them. When Elvis sang "Love Me Tender," he wasn't singing a ballad, no matter what the DJs called it. Look up the definition for yourself and you'll see what I mean."
But, it's not just the DJs. The 1991 edition of the Random House Webster's College Dictionary that sits on my desk near the computer gives the following definitions of *ballad*: "1. a simple song; air. 2. a simple narrative poem, esp. of folk origin, composed in short stanzas and adapted for singing. 3. a slow romantic or sentimental popular song."
So when traditional music people use the word ballad to describe a song like "Matty Groves", they're consistent with definition 2. The DJ describing "Love Me Tender" is just as consistent with definition 3.
Seems to me that "ballad" is just an example of a word that has different meanings depending on the context. For example, until I travelled through Pennsylvania, I always thought the "Dutch" were people from (or descended from people from) the Netherlands. But the "Pennsylvania Dutch" are of German extraction.
Of course, the melody to "Love Me Tender," is "Aura Lee" which many people assume to be a traditional folk melody. However, one recording that I have of it lists it as an 1861 composition by G.R. Poulton.