My memory is poor (altogether possible) or the author is a liar. I'd very much like to see a transcript of Rush saying that.
On the other hand, did he say it sarcastically? You can't put that in the printed word.
The way El Rushbo explained it was that people in the food business told him they needed the labor from south of the border to keep food prices low.
Rush got the flak from the agri-food people because so many callers to his show were speaking out against illegal immigration.