Terrorism is defined as the "systematic use of terror...." If these gang members used fear, which they usually do, then it's a stretch, but I can see it.
I know anti-gang legislation tends to be overturned, but isn't RICO still on the books? In any case, this guy is a grandstanding assclown. For one thing, if the courts say these guys aren't terrorists - and reality check, people, they're not - then these gang members walk free.
You do realize that according to Bush, the proper response to terrorism by Mexicans would be to invade Costa Rica, right?