Yep, from my experience some people will ONLY learn from their mistakes and bad decisions, and won't take in the advice a seasoned web developer gifts them which in my opinion is a very reckless and dim-witted approach to development IMO.
For people like that, arguing won't get you very far so you must show them the errors of their ways, obviously this means more work for you but in the long run the right decision will be made thus resulting in a much easier/cleaner and safer code-base.

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mysql> SELECT * FROM `users` WHERE `users`.`clue` > 0;
Empty set (0.00 sec)