gang members are hardly terrorists compared to the terrorists we're fighting. I'm not going to indicate my opinions one way or another on iraq or anything like that, but just because gang members use violence regularly doesn't mean they're terrorists - it means they're criminals.
Think of a terrorist bombing a building to scare americans. Gang members may use bombs (not that the weapon choice matters much per se), but gang members largely just fight with other gangs. Yes, there's collateral damage (hurt cops, hurt by standers, etc), but generally gangs are only engaging in violence against other gangs that are composed of people who accept that and choose that as their way of life.
(I should note that I'm not trying to say I think we should ignore gangs or anything like that, just trying to explain why gangs are not 'the real terrorists'. I grew up in a heavy gang area, I wasn't afraid of gangs, because I wasn't affiliated with any. They fight amongst themselves, that's different than regularly attacking the general public).