File launches in Launchctl with PID - Status 1
PID - Status 1 means that the process doesn't have enough privileges to access some files (presumably /etc/hosts). To be able to execute script as root, you need to move the loader to /Library/LaunchDaemons or /System/Library/LaunchDaemons 

(processes in /Library/LaunchAgents/ or ~/Library/LaunchAgents/ are run as current user so they don't have root rights).