It might be harmful for some people on the consumer side, depending on their mental health and cultural upbringing. But in general there is no harm. On the producer side there might be harm caused by the way we consume porn, but not by consuming porn in general. Harm comes, when the exploitation of actors and actresses is a calculated part of the business model. So I guess we should be more willing to actually pay for the content that satisfies some of our basic needs - weird thought! On the other hand, I do not really know about how these producers monetize their content. But I know that exploitation of actresses is a hot topic.