Someone learning and practicing magic for healthy reasons probably wouldn't even verbally divulge to you s/he was a practitioner anyway. Something about the person's persona would be more revealing, I think. As an adept would need to work in silence or solitude, it wouldnt be the sort of thing you would just be throwing out there like that, even in hopes of scaring or impressing someone.
Besides, the more power one incurs and cultivates, the greater his/her responsibility and accountability becomes. This person would subject to the effects of forces the average person would not be intuned to.
That being said, to practice in this way, the person would have had to evolved away from practicing from ego.
That is your true black magic, I think. Whenever one approaches magic from the perspective of using it to improve his material and temporal circumstances, he's practicing from the wrong place. Thus, until you get past your ego, any form of magic one practices will be, inherently, dark.
Honestly, it might be the desire for the power to change these things which inititally attracts a person to magic...but if you maintain this mentality as you continue to learn, I think it is definitely not going to end well for you. You're not supposed to be learning how to work within the Universe's forces just to garner stuff like money, popularity or even control over others.