Go to the fake Airbnb listing and scroll down to "Report this listing".
In addition to doing that, you should probably also contact Airbnb Customer Support (change the drop-down menu above from Community Center to Help Center). Someone recently reported a similar problem and said that "Report this listing" did not work quickly enough.
This is completely illegal, notify law enforcement, financial crime prosecution, for lost profits, there are copyrights that protect you, don't let it inflate your problem!