Defender Control is a tiny tool which allows you to turn Windows Defender on or off-- and prevents anything else changing that setting.

The program provides two very obvious "Disable..." and "Enable..." buttons where you can make your choice.

There's also a button to launch Defender, and a menu with an option to control Windows Defender's settings.

You can call the program from a script to disable or enable Windows Defender, as required. Use "DefenderControl.exe /d" to disable Defender, "DefenderControl.exe /e" to turn it back on.