Sometimes it is necessary to do an Antivirus scan while in safemode. I have noticed an issue with Symantec Endpoint Protection. After booting into safemode and attempting to launch Symantec Endpoint Protection, an error appears which says "It appears that the Symantec Management Client service is not running. You will not be able to manage network protection settings through the main user interface until it is running. Do you want to start the service now?"
It seems you would want to say Yes, but that will not work. You must choose No. Then the user interface will load and you can scan. You may receive a notice about realtime protection being disabled. For this purpose, that can be ignored.