From looking at their CSS, it might be this line of code: -webkit-text-size-adjust:none;
If so, it'd only work in a limited number of browsers, not everywhere.
There's not much reason you should be preventing users from adjusting text size, though. Yes, it might cause problems with the design, but you could also argue that the design should be flexible enough to deal with font size changes.
Comedy option: replace all your text with images.