I think porn is really very like alcohol. The odd amount enjoyed responsibly isn't an issue, if you want to that is (nothing wrong with being teetotal either!) but becoming dependant on it or addicted to it, or allowing it to desensitise you to the real world, that's when it's dangerous. As such I wouldn't recommend it as a "go-to" distraction in relation to depression, as using it while in a vulnerable state of mind is going to increase the negative effects.