Uninstalling any Anti-Virus product can be a pain for obvious reasons with Symantec Endpoint Protection being no exception, the following PowerShell command is a simple one-liner that can easily and quickly remove it without the need for a reboot.
Run PowerShell as Administrator then paste and run the following command
(Get-WmiObject -Class Win32_Product -Filter "Name='Symantec Endpoint Protection'" -ComputerName . ).Uninstall()
After a few minutes the Symantec AV should have been uninstalled, you can verify this by checking the Symantec Endpoint Protection service has been removed. A reboot is not normally required.
This command has been tested with version 12.x but has not been tested with Tamper protection turned on.
If this fails to work, run the Broadcom Cleanwipe utility which will remove it but will likely require a reboot.