Why has the word Liberal been turned into a bad word, when it means being open?

Just curious of when this word got twisted into a dirty word?

By the way, I'm not a democrat and not a republican.
Update: what is a sp?
Update 2: Wow. I'm getting some great answers. It's going to be hard to chose.
Update 3: I mean choose. :-)
Update 4: I especially like the answers that are impartial to Republican or Democratic views. It's very Liberal in the true sense of the word.
Update 5: I wish I could edit to use the lower case liberal now, but I can't.
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