A carefully considered and sensitive critique can only help the author of the work being reviewed although there are times when an almost savage destruction can work too. I think respect is probably an essential element here, the author needs to respect the critic and vice-versa.
My work has been savaged by high profile photographers and teachers in the UK and I'm convinced that the critiques were a turning point in the development of my photography. At the time of the critiques I was hurt and felt that I was inadequate and a failure. However, after reflection I realised the sense in what had been said and my photography moved forward. The three photographers in question, John Blakemore, Paul Hill and Thomas Joshua Cooper are good friends who I respect very much and they still guide and influence me.
I frequently look for comment on my images from non photographers who view them with no baggage relating to phototechnique etc., and find their views refreshing for they are responding only to what they see and that it often totally different from the way that I view the image. I think it is essential that we are all prepared to look for, and accept, informed comment on our photography.