I suppose I was not as rigorous as I could have been ... you are right, it is far better to set font size by 'pt' rather than by 'px' for flexibility. Generally the font-size setting scheme should strive to be a base font (your "normal" text, specified in the body tag) with a 'pt' specification (or no setting if the default suits you) and then using percentages to set other font sizes relative to it. This allows the whole page to scale well with minimal effort.
If this sheet were to become the basis for a CSS Perlmonks site, it would need careful community scrutiny. But for specific "I don't like that" complaints (not saying yours is such a complaint... you have a very valid point) people will still have the opportunity to override things with their own style sheets.