Then what they should have done is tell the host who volunteered "It is very important that this event will be free of harassment", and he would either have agreed or have said "Oh dear, I wasn't aware of that! I'd better quit!"

And as I wasn't there, they may well have told him and I don't know.

But accepting someone and announcing his name and then watching lots of individuals who behave like a mob shouting "But this means there will be harassment! Everybody knows that!" until the person steps back - no, sorry.