The logic is obvious, surely. I'd like to hear why you think otherwise. Imagine anyone with poor sight, trying to read small fonts set in pixels on a site. In IE, they are stuck - they cannot up the text size. In all other main browsers, they can, and quite easily. (In Opera, you just press + on the number pad.) So then the person can read the text easily. What can possibly be wrong with that?
Or to put it another way, why would it be right to stop them resizing the text? I don't get it.
Besides, all other font types can be resized, such as ems and percentages. So why should pixels be left out? Because of some stupid decision by Microsoft, that's the only reason.
Unless you are wishing to retain the layout? Sorry, the web is a dynamic medium, not fixed like a printed page. Browsers like Opera allow us to change a page completely - alter the colours, images on or off, styles on or off etc. So why not font size? (I agree Opera's Zoom is the best solution, but just resizing the text is the next best thing, regardless of whether it ruins a 'perfect' layout or not. Text simply must be readable for all people, else the web has failed.)