The word is not really a legitimately formed word, and I'm pretty sure both are correct (or incorrect, depending on how you view it). The OED lists both uses (all condescendingly). I remember reading about 'beautician' (Fowler?), and how ridiculous they made it seem. Generally, the -ician suffix is reserved for words ending in -ic (etc.) Mathematic(s)-> mathematician.Readers of this blog reveal new wells of information all the time.
I suppose I can understand usage experts' disdain, but what the heck do you call the person who's an expert on meal planning? The diet guy? The diet dude? Diet-woman the magnificent?
I mean, come on. Sometimes, inelegant uses persist because we don't have a better alternative. AP's mention suggests they haven't figured out a better way.
The reader who left that response has an interesting usage blog. You can find it here. The creator promises "some of the most boring, academic pedantry on the web." Who can resist?