You don't know that the person didn't get it from another website which claimed the image was under a different license. Or hell, the person could even have paid somebody else that had copied that picture and included it on a batch of stock images they had no rights to.
Irrelevant. All off those are possibilities, but they are NOT get-out-of-jail-free cards. "I didn't know it was a stolen image" doesn't follow with "so I can keep using it" any more than unknowingly buying a stolen laptop on Craigslist mean you get to keep it if the police find it.
Basically, you can't assume that the person knows they are infringing copyright.
Irrelevant. There's nothing in here about intent. People were using Jeff's images unjustly. He followed the law that covers how to deal with that. Period. They how have to stop using them. Period. One sociopath has a problem with that, and that's why we're hearing about it.
Once again, not a lawyer, but it's my understanding that for any civil disagreement, if you show up in front of a judge without first having tried to negotiate and resolve the conflict amicably, the judge is going to be very angry at you, and tell you go try to negotiate first.
Irrelevant. Jeff isn't suing anyone. Jeff isn't taking anyone to court. Jeff is following the law when he issues a legitimate DMCA request. If Jeff ends up in court through some travesty, that's what the judge will care about. The only person talking about going to court is the nutjob who stole his image. And if you want to see a judge get mad, let me assure you that "you used an infringing image, the plaintiff filed a legal and appropriate injunction, and you're suing him because you don't like it, and you're a lawyer" will result in a full-blown melt-down, if not a formal sanction and request for disbarment.