I don't know much about straight edge but here's some stuff I do.
The name, and I suppose the movement itself, comes from the Minor Threat song of the same name and was a reaction to the prevailing attitudes within the hardcore punk scene in the late 70's early 80's. The most obvious of these are the drugs and alcohol issues. It also included at the start, promiscuity and racism as major issues to fight against in the scene and later included animal rights, veganism and such
The group FSU, which nows stands for Friends Stand United but was originally fukk shyt Up was formed to ''attack, beat and purge drug users and violent White supremacist, Neo-nazi, Skinheads and other various racist gangs from punk rock concert''
Straight Edge to me, seems to be inherently anti-racist amongst other things and can't just be defined as a non drinking/drug using. It's about a lifestyle, the music, social justice and all that lark, racism doesn't fit and a lot of these people don't seem very tolerant of people that call themselves straight edge but don't ascribe fully to the lifestyle and it's beliefs.