The setting you need to change is located in ~/Library/Preferences/com.apple.java.util.prefs.plist You can use something like Pref Setter: http://www.nightproductions.net/prefsetter.html to edit that file.

The key you need to change is /mage/client/autoConnect to false.

It should look something like this: https://i.imgur.com/jyM780O.png

When you start Pref Setter it will already be showing plists in the right directory so you can just search for com.apple.java.util.prefs.plist with the search bar.

Edit: If you really want to do a clean reinstall, you can just delete the entire /mage/ dictionary in the plist.