Hm... well. I think - if you steal art, you definitely know you are a hack then
About being a hack or an artist... I think that's a hard point to be defined. Art is so much more than "just skill". You know - there are very skilled people, that just aren't really artists. They can copy a lot, but not make things up for themselves. On the other hand - there are artists with great ideas, but (yet) they lack the skill to get things down on paper/canvas/whatever.
In my opinion, an artist should also be skilled. I do not really like all those people today that, sorry for the upright saying, just make some blotches of paint on a canvas and call it art! I do believe that many of those lack some skill (though I'm not sure). If you have the skill, and know what you are doing - and then break out of certain rules, it's more okay for me to see those people as artists. Because they know what they are doing, and they know "the basics".
Another factor of "art" is society itself. There are several kinds of "art" that I do not relate to, or think "wtf - why?". But - knowing the cultural context I do see why those things are marked as art. Like someone putting empty cartonages upon each other and declaring those as an artwork (I forgot the name of the artist, but he's rather famous - that was in the 50s or 60s I think). It's something I would not pay an entry for, or even want to have a look at it. But - what he did "broke" the established rules of art, and thus broadened the whole field and what is possible. There are various examples for that - like impressionism or expressionism (they are somewhat close related in my head - it's a while since I read/learned about them). Those artworks were not part of the "mainstream", and if I remember correctly, they were "smiled upon" - something like that. But that kind of art changed the way people see art, and established a new kind of depicting things. And that's the reason I acknowledge them as art, and can appreciate what was done, even if I just shake my head on it or don't like it.