Screamo is not an actual genre. It was a term used by ignorant people who have no idea of what emotive hardcore is. Emo is emotive hardcore, and is just that, a form of hardcore, hardcore can have screaming, therefore, another genre(screamo) is redundant.
And if it were a genre, Alexisonfire, coheed, and all that garbage would not be part of it. It would be Swing Kids, Antioch Arrow, JR Ewing,Envy, etc.
Kid 1: I got the new Alexisonfire cd. Man I love screamo.
Kid 2: You're an idiot.