Absolute voting frustration!

Here in OR we vote by mail. I just got my ballot and suffered an enormous shock - I can't vote in the May presidential primaries! I can't vote for Dennis :( This is because OR has closed primaries (I think it's called closed) which means that if you're not registered Democrat, you can't vote in the Democratic primary. What a crock of shit! I remember hearing about this but I didn't realize what it meant. That sucks.

In a larger view - who thought this up & why? This totally disallows a whole bunch of people from voting in primaries and that seems absolutely unfair. If you know the answer, will you send me email?