We're all artists. Being artistic means to be human, to express opinions or feelings; everyone does it, some more creatively than others, but that doesn't elevate them to some kind of higher status. If someone publicly and loudly declares him or herself as an artist in an attempt to draw a distinction between that person and the audience, you'll know what he or she's actually trying to say: "Hi, I'm having an opinion and it matters more than yours." And that is bullshit.

There's a reason art lies in the eye of the beholder: You as the viewer agree to the artist's opinion or not.

I recently read an essay by James Baldwin, who said artists owe their audiences the truth, to hold up a mirror to society; they are "incorrigible disturbers of peace". Guess what, everyone owes him or herself the truth. You shouldn't be lying to yourself or anyone else.
  
I also saw a keynote by Trevor Paglen and while the video itself is highly interesting, he starts off by introducing himself as an artist. Why even bother stating that? He said he's not the painter type artist either. So in plain English he said that he loves to show truths about the world. Why he's bothering to set himself apart from "mere" painters - it doesn't make sense other than to try and convince people that he is even better and more important than them. The only difference I can see is that the painter already fits an established category and he does not, and maybe he's scared that he won't get recognized by humanity if he doesn't belong to at least one category of this world.

You probably shouldn't call yourself an artist if all you're trying to accomplish with it is to push your ego. It's not supposed to be a badge you wear in an attempt to show everyone you're a Very Important Person.

The best artists - the most successful human beings - are people who stay true to themselves, especially to their inner child. So when people say some guy is a true artist, does that mean he is simply talking and sharing absolute truth about everything?

Everyone is an artist. Everyone is human. Stop lying to yourselves and you'll see it too.