Art theft is upsetting to any artist, whether its theft of their work or someone else's. This often causes deviants to lash out and attack the one committing theft, but this is not a good thing.
Here on dA, stealing art is a bannable offense. Harassment and abuse, are also bannable offenses. I have seen people go to town on a person, leaving nasty comments and sending in ban inquiries before the deviant even has a chance to react.
What we need to keep in mind is that not all of these people are purposely doing this, I've seen several cases where it was not maliciousness, just ignorance.
Harassing someone who is oblivious to the rules, giving death threats, spamming, and any other form of harassment is NOT going to solve the problem of art theft on dA.
We should be giving the benefit of the doubt to these people. Be compassionate, don't just shoot and ask questions later.
I feel the best way to approach a deviant who posted copyrighted works is to NOT report anything at first, just warn them and ask them nicely to remove it.
If they refuses to take down the work, and swears up and down they made the works, THEN start reporting works, and writing ban inquiries. But do not, under any circumstance, harass these people! It's not worth getting yourself banned over!
Just remember, BE DIPLOMATIC, and don't attack until you know for a fact that the person is doing it on purpose.
In regards to the frame of mind that "the admins should be doing this, not us"; Take into consideration how large this community is. It's like a major city, and the admins are the police force. They can't be like the gestapo and hover over everyone's shoulder CONSTANTLY, and to be honest I LIKE it that way. Just like any community, city, or street, you have to contribute to keep it clean. We have to work TOGETHER to keep the crap out.
We are not e-thugs, we're just fellow artists, neighbors, who want to take care of their community and help it grow.