The Ashkenazic custom to refrain from kitniyot developed out of agricultural and climatic conditions and developments that were particular to those communities. It is not the result of some sort of communal neurosis.
That's the gist of the brand-spanking-new theory of kitniyot that I just posted at the Times of Israel.
Enjoy, and please consider sharing that post with all those grumpy Ashkenazim and all those who think this custom is nonsensical.
Hag kasher ve-same'ah.