To stop users from disabling SEP on any components of sep you need to do the following:
1. Open the Antivirus and AntiSpyware Policy
2. Click on the file system auto-protect.
3. Lock all the options using the Lock icon.
4. Lock all options under all tabs (like : action, notification etc)
5. Repeat the steps for all others (like : Internet email auto protect, etc.)
If any one of the lock is open, the user will be able to disable atlease one of the options.