Do dolphins ever fight each other?
Yup, they will actually kill weak members of the pod or others they don't like, including infants and juveniles. They more commonly kill other types of dolphins and porpoises, but have also been documented killing within their same species. They also appear to kill for pleasure in some cases. Dolphins are jerks.... but so are some humans.
There's video out there of them doing this, I saw it on a documentary once years ago, but youtube is coming up empty. Only found videos that really don't show them doing much. In the documentary I recall them breaching and ramming each other right in the mid section, and it was the whole pod doing it to one dolphin. It was sad. :(
Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins engage in such acts of aggression apparently for the same reasons as humans: disputes between companions and competition for females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile as a result of losing a fight.
Male bottlenose dolphins have been known to engage in infanticide. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins, and are therefore not competitors for food supplies.