No, giving people a free pass ("may be fair") to lie is not acceptable, even if lying is expected and commonplace. It's still dishonesty and is supremely unprofessional.
Re:Twitter announces layoffs
by jsprogrammer on Tuesday October 13, 2015 @05:56PM
(#10383765)
We can still recognize it as being dishonest and unprofessional. One must meet the criteria of being dishonest and unprofessional before we can label it as such.
The fairness is in the labeling (we do not want to unfairly label those who were not actually dishonest or unprofessional; sometimes mistakes do occur), not in the response to the behavior.
There would be no reason to make disclaimers otherwise.
It's a form of the, "I'm not a racist, but...", style of argument.