In the end, there are no bright shining lines in psychology. It is likely that psychopaths are on one end of a bell curve rather than being a distinct, binary pathology. Neveretheless, we are free to observe that there is such a dimension and discuss those on the extremes in certain ways using certain terms, just as we do with depression or OCD, both of which have the same characteristic of not having a "bright line", yet clearly existing.
One of the most powerful ways to understand psychology is to see its history, like math's history, as one long attempt to create and refine definitions that let us discuss the field. Except where math is using those definitions to create the field from scratch and the effort is to build up useful systems from the bottom, psychology is trying to understand an incomprehensibly complicated system from the top down and using those definitions to try to break things into comprehensible and consistent pieces in a landscape that is being aggressively fuzzy and resistant to classification.
I do find myself wondering if you have not encountered any apparent interviews or research on psychopaths not because it doesn't exist, but because you've never gone looking for it. There's quite a bit of it. There's still some professional skepticism on the topic of it being something distinct, but that's rather different than the skepticism you seem to be expressing. The phenomena aren't so much what the debate is about as what the best way to slice and dice it up with the definitions are. For them to professionally agree that psychopathy is a real thing carries additional implications beyond just what Merriam-Webster writes in their next dictionary edition, but it's easy for a layman to misread that as an argument about whether the phenomena described by the debated term exists.
So, of course it's a label. But it's used to describe something far more different-than-baseline than just being a plain ol' jerk. In fact, psychopaths are often not jerks at all. "Jerk" is usually used to describe someone openly abrasive and simply randomly hostile, and that's not what a psychopath is. At least, not as an adult. As the article says, they lack emotional empathy but develop a cognitive empathy, and generally learn by adulthood the thing that jerks never do, which is that open hostility really has no advantages to anybody. They learn far, far more subtle manipulation techniques than that. (We all learn how to manipulate; I'm not convinced they are "extra skilled" at that. They simply learn how to do it with one less constraint than most of us.)