It seems like people do not pay attention to details... If the OP's friend was denied entry once, it may very well may happen again, and it has nothing to do with the fact that in general, Canadians do not need visas to visit USA. I guess, the worst thing that could happen is he would be asked to withdraw his application for admission again and allowed to proceed to his connecting flight to NRT (instead of sending him back to HKG). Firebug4 could perhaps shine the light on this issue.