I had the very problem yesterday evening, so in case you did not figure it out:
To disable the Google feed if the disable toggle disappeared just clear the App data of the Google app to make it reappear.
To disable the Google feed if the disable toggle is present but has no effect anymore you can log out of the Google app by deselecting your Google account in the "search" settings menu.
I'd spend hundreds to avoid any kind of feed in my os.
It doesn't work for me. It is so frustrating. I live in Catalonia (Spain) and politics has been so intense here these last months that I want the right to disconnect from politics, but I can't, because I can't disable the news cards in Google Now.