Here's another fix that works for many people, which doesn't require you to remove files, use Terminal, trash all your network settings, downgrade system files, etc etc.:
The problem is with any PPP (modem) configurations in the Network prefpane (and possibly PPPoE configurations too), for which the "Save password" option has been selected. The Security Update changes the way PPP passwords are saved, but didn't implement the change correctly. This procedure fixes this for each of your PPP configurations, by deleting and re-saving each of your PPP passwords.
If you don't know what the passwords are for your PPP configurations, don't follow these steps, because the process will wipe them out, requiring you to re-enter them. As pointed out in a couple comments above, you may be able to see your PPP passwords using the "Keychain Access" utility, in the Utilities folder.
• Open the "Security" prefpane, and select its option "Require password to unlock each secure system preference."
• Click on the "Show All" button, then open the "Network" prefpane.
• From the Network prefpane's "Location" popup, select the first PPP (modem) configuration that's listed there. If you're not sure which ones they are, select each Location one at a time, and from the "Show" popup below the "Location" popup, select "Modem port" (if it's not automatically selected), and see if there are any settings entered (telephone number, etc.). You're going to be operating on any Location configuration that has its "Save password" checkbox selected.
• Click the lock icon in the lower left corner labeled "Click the lock to make changes", to unlock the settings, then enter your admin password.
• De-select the checkoff for "Save password". In the "Password" field, re-enter the password for that PPP configuration, then re-select the checkoff for "Save password". Then click the "Apply now" button in the lower right corner.
• You can leave the lock icon in the lower left corner unlocked if you wish.
• Follow the same steps for each of your Location configurations that are set up as PPP (modem) configurations.
• When you're done deleting and re-entering the password for each of your PPP Location configurations, click the "Show All" button, then open the Security prefpane, and de-select its option "Require password to unlock each secure system preference" (if that's how you'd like to leave it).
• Close System Preferences, open it again, then open the Network prepane again to test the fix. If you don't get the annoying message any more about your network settings being changed by another application, re-select from the Location popup whatever Location configuration you want to use for connecting to the Internet, and close System Preferences. If you do get the annoying message again, try another technique described in this thread.
I think you're a bit over the top when you say that Apple's negligence in providing a fix for this problem, means that Apple doesn't want to be in the computer business, and doesn't want us around. Apple wants to be in the computer business, even though Apple has often been slow to release bug fixes for years (and sometimes never does, at least until some future OS update)--but this is also the way many other major computer companies, including Microsoft, often do things. I'm not sure why you think you'll get any better results with a Windows computer.