Rape and sexual coercion has been observed in many animals and is hardly unique to dolphins. If you look at humans we display horrific behavior on scales no animal is capable of especially to our prey(which may include humans). Dolphins are aggressive predators and sexually aggressive as well, but I don't think it is reasonable to judge other animals using human morality. Dolphins exhibit altruism helping injured and dying members to stay afloat. Dolphins are able to communicate through vocalization with each other and are able to exhibit multigenerational social learning. Dolphins also exhibit other undesirable behaviors like infanticide. It's important to have a nuanced view on the world and banish black and white moralism.

I think it is import to respect animals and nature for what they actually are instead of what you want them to be, but for symbology most people don't think rapist when they see a dolphin.