I am having trouble with this again now that I have upgraded to ArcGIS Desktop 10.5. I must have had settings that were not preserved in the upgrade. I don't remember how I solved this last time. Still running Windows 10 Pro. I don't see a way to uninstall IE, 11 in my case. It doesn't show up under "Add or Remove Programs" and isn't it intertwined with the Windows OS? I have gone through all the IE internet security setting as explained in Problem: Issues with ActiveX controls when launching ArcMap , restarted ArcGIS, rebooted, still have the problem.
Update: I did find a way to uninstall Internet Explorer 11 in Windows 10 by going to Windows Features. How to Uninstall IE11 From Windows 10 Still have ActiveX warning messages all over Arc Tools. Even with IE uninstalled, the system still has Edge installed, and there are still the same Internet Properties>Custom Level>Security Settings to deal with.