I didn't think this was possible. I've not tried _Brian's suggestion myself, but Symantec suggests you disable the uninstall password first () as per:
http://www.symantec.com/docs/TECH105827
What version of SEP are you trying to remove? If it's an older version, then the below might help:
https://www-secure.symantec.com/connect/forums/how-uninstall-symantec-endpoint-protection-sep-client-silently-using-command-line#comment-2270331