In situations like that, you should be reporting him to the owners of the server - in this case, it's an AirAttack server.
Go here:
http://airattackteam.com/forum/forumdisplay.php?fid=32
Start a thread, and fill out the following info:
Your LFS Username:
Offender's LFS Username:
Description of the incident:
Replay / Screenshot link:
Replay timestamp(s):
You'll need to supply the replay file too, so we can verify the hacker's username.
We'll make sure he doesn't come back for a few years...