The Golden Rule? How would you like to be treated by a GM?
My own answer (for either side of the game) would be that it depends... If i have time and am in the mood for it then a lesson would be great. Otherwise best to just get it over with.
no simple answer overall.
One would like to encourage newbies rather than drive them away.
When I'm playing against someone that I don't know very well and I'm winning, it seems so cruel. It's more than likely that they just know how to move the pieces, learning about en passant, that sort of thing. I mean, I would have just met the person. Just picking off their pieces one by one. There seems to be no point in 'going easy' on them seeing as i'm not going to actually let them win (how would you go about doing that without them catching on?). How do you play against such an opponent?