How to uninstall Docker completely from a Mac?
Start Docker. Go to the Docker Preferences from its menu bar icon. Within there is a 'Power Button' icon labeled "Reset". Click on that and then click the "Uninstall" button.
To uninstall Docker Toolbox from Mac, first simply download the following Docker Toolbox Uninstall Shell Script to your local machine.
Use the Terminal application on your Mac (i.e. Press CMD+Space to open Spotlight Search and enter keyword "Terminal") to change into the directory it was downloaded into (i.e. cd ~/Downloads), and then execute the file with sudo bash uninstall.sh.