Is there a way to delete all your contacts off a device that's on a BES, without deleting them off the BES/Exchange server, and then, after the contacts on the device are empty, sync anew from the BES?
Yes, but it takes several steps.
1. Contact your IT admin and make sure they have a current backup.
2. In the Address Book, press Menu / Options / Desktop and change Wireless Synchronization to No.
3. Connect your device to Desktop Manager and navigate to the Advanced Backup and Restore screen.
4. In the right-hand window, select Address Book, then press the Clear button at the bottom of the window.
5. Reverse Step 2 to restore Wireless Synchronization to Yes.
6. Contact IT and have them push your Address Book database back to your device.