The only time I would ever flame anyone, particularly a n00b, is when they make comments on maps that aren't of any use to anyone, or act like they are the king of mapping and therefore have the right to tell people their work sucks, despite the fact they have no experience or work of their own.
I was, like everyone else, a n00b once (about 4 years ago). But, like most n00bs, I knew my place, graciously and gratefully accepting usefull advice and criticism because the people with experience generally knew more than me. It's only when they get too big for their briches that they get flamed.
To my knowledge I've only partially flamed one person on this site, and more than likely it will be the only person.
I think the best option in this case would be if you haven't got anything nice or constructive to say, don't say anything at all.