SEPprep: http://www.symantec.com/docs/TECH148513
You may want to try SEPprep utility. Its a competitive product uninstall tool. But it can also be configured to uninstall SEP Client by modifying the following line in the SEPprep.ini file.
RemoveSymantec=Y
You can push this to the clients through GPO (like a logon script) or using a deployment tool.