Lately I've been listening to a couple stations on iTunes Radio that include some screamo bands. Probably much to the demise of my mother, I see some appeal to the genre.
I don't know that I actually enjoy the screaming, but there is something cathartic about the tension that builds up until it finally resolves with a melody. To me, it is similar to the dissonance and resolution in jazz songs (yes, I just compared screamo to jazz). It also mirrors the ups and downs that life brings us. There are grating, scarring, painful lows, then soaring, melodic highs.