I don't think Eliezer was suggesting that contamination be "eliminated." (That's probably not even possible without physically modifying the brain--as Luke points out here, we are essentially built out of cognitive biases.) Instead, he's arguing that we need to be aware of our own thought processes and notice when our brains come to a conclusion because of a priming effect; this allows us to correct for the contamination and make more accurate estimates.
ETA: Biases that cannot be totally eliminated are usually still worth reducing.
Today's post, Priming and Contamination was originally published on 10 October 2007. A summary (taken from the LW wiki):
Contamination by Priming is a problem that relates to the process of implicitly introducing the facts in the attended data set. When you are primed with a concept, the facts related to that concept come to mind easier. As a result, the data set selected by your mind becomes tilted towards the elements related to that concept, even if it has no relation to the question you are trying to answer. Your thinking becomes contaminated, shifted in a particular direction. The data set in your focus of attention becomes less representative of the phenomenon you are trying to model, and more representative of the concepts you were primed with.
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