Is very easy, apparently. Even a simple photograph, which is no more than a faithful recording of a fact, could offend. In this case a picture called "New Mexico," which shows a mesa with portable toilets in front of it, appears to be offensive to some.
I can't see what's so offensive in this picture for the life of me. As a tourist with some accumulated mileage, I have been in much more offensive situations, not the least of which was a mesa without a chemical (or any other) toilet.
So, I think, some people should just relax.