If it's 'constructive' and 'criticism', it is an Oxymoron. However, 'constructive' is really tag picked up voluntarily and the process is purely subjective. If ever someone feels hurt, he should leave the field to the others. There is really concept known as 'Swakucha mardanam' that implies self-gratification (because none else is coming forward to do it, without having hurting). A discussion or even a forum for it permits no self-centered human emotions.