NPR: What Drives Men To Violent Extremism.
One is in their teen years in high school when they feel lonely, isolated. School's not working for them. They get bullied and beaten up. They have no friends. And along come these sort of skinhead guys who say, hey, hang with us. And they feel that community and connection and validation of their masculinity.
There's your answer right there. Wrong 'community'. This can be solved.