This works: diskutil corestorage delete

two scripts to fix it:

Apple script that calls a bash script.

Disk utility apple script:

tell application "Terminal" activate do script "sudo ~/Documents/diskutlityfix.sh"

end tell

Bash script that deletes the core storage

#!/bin/bash
#----------------------------------------------
# Disk Utility FileVault 2 - Version 2
# Javier Arzaga
#----------------------------------------------

LVG=$(diskutil corestorage list | egrep "Logical Volume Group" | awk '{print $5}')

echo "Are you sure you want to erase the drive? Type: Yes, followed by [ENTER]:"; read answer

if [ "$answer" == "Yes" ] || [ "$answer" == "yes" ]; then diskutil corestorage delete $LVG echo "The corestorage drive: $LVG was deleted" else echo "Have a good, Day!"
fi

I'm having no trouble erasing encrypted disks with that version of Disk Utility. Maybe post a screenshot of what you're seeing in Disk Utility?

Are you referring to the inability to erase encrypted disks without knowing the password? This was a "feature" added by Apple in 10.8.2, and is considered normal behavior now. If you attach the Mac in target disk mode to another Mac and try again, it will allow you to erase the disk without needing the password for the drive.

Have a good, Day!