You cannot hunt them down physically.
But you can spam their blogs, FB, Youtube clips the same way they spam other peoples blogs.
Ridicule, and scaring them that time is up for them and they are about to become the laughing stock of the world because the promoted the 2012 and it failed! Don't threaten them with real physical danger or directly. But tell them that in less than a month they will be exposed as frauds, liars and creepy guys and they will have a lot if pissed off followers. Also that they will lose their friends that they scammed for fun.
Don't waste time in debating them, just every day tell them that they have 27 days left until they are exposed as fraud. 26 days left when they will be exposed as frauds, 25 days left that they will be exposed as frauds. Use the same count down trick they use. Make up imaginary story's telling that Nibiru is failing. When they claim they did not put a date on it, ignore that and keep on pretending that they did claim the end would be on 21 Dec 2012 (In reality they did put a date on it, they are just covering their tracks because it is very clear that nothing is going to happen). Use the exact same techniques these people did on you. If they explain why Nibiru does not show up, ignore that and make up a new claim that shows that Nibiru is not coming. Call these people sheeple and tell them that you are searching for the truth. Yell at them that they provide disinformation.
With a little bit of luck you will attract more followers that will question these people and these people also start to fight back when they realize that they have been scammed.
People stop being a victim and fight these scammers and doomtards back. Take back your life. And with a bit of luck you will also save other people from harm right now.