The full command on Windows would be "Unreal.exe Vortex2?mutator=Tourism.Tourism", the first bit there is the EXE the shortcut is running, everything else goes in the arguments field if I'm remembering the Windows shortcut properties window layout correctly.
If that launches into the game's first level but you still see enemies, make sure the Tourism.U file is in the same dir as your Unreal EXE. If it launches into the menu, something isn't right about the command line arguments.