Why is it there is an expectancy for the "positive" emotionally related attitudes but any which are deemed "negative" are expected to be left at the door. Either one is engaged or not. No-one can selectively choose which emotions to apply. Either you are emotional about your work (passionate, enthusiastic etc) or you are dispassionate (not necessarily a bad worker but rarely exceptional).

Professionalism is a totally different facet of an individual i.e. unrelated to the emotional status.