Harden Batting from the Left side

In Friday’s game Rich Harden was facing left hander Cliff Lee. I noticed that Rich Harden is a left handed hitter. I knew that he batted from the left side, but assumed he was a switch hitter like Zambrano. I dislike pitcher’s who are switch hitters and expose their pitching elbow, but how did a right handed pitcher start batting from the left side? He isn’t a good hitter from the left side, so maybe he should try from the right side?