From a look at their CSS, it could be this line of code: -webkit-text-size-adjust:none; If so, it will only work in a limited number of browsers, and not everywhere.
There are not many reasons why you should stop users from resizing text. Yes, this can cause design problems, but you can also argue that the design must be flexible enough to deal with changes in font size.
Comedy Option: Replace all text with images.
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