Not only is it not telling the truth, but it is making people have severe body image issues. As far as I'm concerned, almost every picture of a model or celebrity is photoshopped in some way, especially those on magazine covers and billboards. This makes it very hard to be happy with your normal self, and gives many children false aspirations of what a person can/should look like.
This relates to journalism because we are always trying to tell the truth. It would be easy to do a story on photoshop manipulations that people see daily, or what local magazines and advertisements in your town are using photoshop manipulation. Also, if you are a photojournalist, it's important to not photoshop your pictures!
Here's a great Web site that shows celebrities who were manipulated in photoshop,