If you would supply me with the license plate number of your snowbird thoughtless friend I will be happy to forward it to the Georgia Highway Patrol because in Georgia the left lane is strictly for those who are passing, after which they are expected to pull back into the right lane or be issued a ticket.
Other than that if I found myself on a 65 mph highway with someone going 45 mph in the fast lane I would call 911 and report him as a hazard to road safety.