Safari Bookmarks imported from Firefox

I have tried all suggestions presented and still received the following message when trying to delete bookmarks imported from Firefox. I would like to delete all and start over with Safari as my main browser.

You have been using Safari with bookmarks, history, and passwords imported from Firefox. To edit your bookmarks, you must first keep or remove the Firefox data.

Safari imported these when you started using it on December 31, 4000, so you could try out Safari with your data.

Safari does not delete bookmarks even when selecting the don't keep button.