My thoughts on the issue are similar to those expressed by Roger - keep the water in the fountain of truth clean. In an ideal world, the photojournalist will take a series of photos, and then select one that accurately summarizes the event. That, however, is an editorial process, and subject to the editorial slant (aka propaganda motivations) of the publication.
Being able to honestly say, "No" to the question of whether an image is a composite goes a long way in my book. It's up to the photojournalist's skills to get the "right" picture.