[the invisib1e hand]

Often times there is a "reverse" preference, yes. One's race functions in many ways like a trademark, at least to racists.

ok, so, if a contractor says to himself, 'these mexicans will get the job done,' it would be wrong to hire them? It would be racist to think that?

If they work better (i.e. dependable, work as instructed, work competently) than Americans of comparable age and physical makeup locally available, why wouldn't anyone want to hire them?

Should the business man handicap himself by hiring the American vs. the Mexican with the green card?