Yes, because perfectly legal behaviors can still be very alienating, and the homogeny that results from alienating behavior shows a lack of foresight on the part of conference organizers and the open source scene in general.
You asked a simple question, why is a harassment policy necessary when laws should be sufficient, and I gave a simple answer, because perfectly legal behavior can still be alienating and damaging to the success of social structures.
Yes, because perfectly legal behaviors can still be very alienating, and the homogeny that results from alienating behavior shows a lack of foresight on the part of conference organizers and the open source scene in general.