Windows Defender running with Norton 360 turned on

Windows Defender turned OFF by Norton 360 still runs and disallows setup.exe to run with no option to run setups. Screen: Microsoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk. The only choice is: Don't run. This results even after Norton 360 turned off Windows Defender. Can't turn off Windows Defender because Norton has already turned it off.