Wow. After reading through this thread, I really feel for you and sympathize (both for your experience with the dog and with the clueless owners here). Our 8 month old English Mastiff has similar aggression issues. We have spent many hundreds of dollars with trainers (training him AND us) using 100% positive methods (no collars), and Goober is only getting worse. We don't have the luxury of leaving the dog to play in a yard in the exurbs all day and just lock him up in a crate or the basement when someone comes to visit until he grows out of this "natural phase." We have no yard, so every potty break is on leash in the middle of the city where we live, and at 125 pounds it's getting quite difficult to fight his urges to go after every cat or squirrel he sees. The bad part of course, is when you turn a corner and there is a five year old tearing toward you on a trike all of a sudden. Or an old friend sees you and comes in for a hug only to get lunged at (hopefully only lunged at). Of course, keeping him on a short tight leash just makes it worse. What to do?
I suspect it's true just getting an electric collar and trying yourself may not be the most productive, especially since like us you obviously aren't being wildly successful with training already. We're going to send our boy to boot camp for at least two weeks where they DO use an electric collar, and we're going to have them train us how to work with him when he gets home. Neither we nor Goober have the luxury to just wait this out. If it isn't dealt with now he's more likely to end up being put down for chasing a kid into the path of a car or biting someone.
Judge away people. We will have our dog peaceful, happy, and ALIVE.