No need to Master Reset....
Use PIM backup. It can delete all your contacts.
1. Download Pim Backup
HERE.
2. Run PIM Backup
3. Go to Options
4. Click Delete All
5. Choose Contacts.
Why would you say to hard reset just to delete contacts? Seams like a lot of work for nothing.
I see this becoming a answer for a lot of things lately, not cool if it can be fixed easily.
I know I wouldn't appreciate being told to wipe everything out if it wasn't necessary...............................