I am sorry that Charlie suffered from a dog attack. So did my boy Alfred when he was about a year old. I stupidly went to a dog park where people tended to be a bit lazy and let their dogs play without really trying to control them in any way. I was trying to socialize Alfred and figured this was one option to add to our other methods. Big mistake! A family pack of three Huskies decided to play rough with him and basically beat the s*** out of him although never drawing blood. The owner just said they were playing despite my repeated requests to have him call the dogs off. I ended up having to kick one of the dogs. Alfred ended up quite traumatized. I tried going back just to make him get back on the horse so to speak. But he hated that place and became fear aggressive. It took quite some time before he became less fearful of other dogs. And then his best friend who had visited him for weekly play dates for a year or more, decided to attack Alfred in our own yard. Alfred made the mistake of lying too close to the Rotties's mom. This was a full-out attack with blood and fur flying. And Alfred's opinion of other dogs plummeted even further. That was over 4 years ago. Alfred and I go for an hour long walk everyday with it usually being in an off leash forest where, happily, if he doesn't like someone he can just avoid them. Over time he has mellowed out although I still keep an eye on him because He does tend to have a shorter fuse than he used to. Happily, to date it is just growling and threatening posture. But it is sad that I must be concerned over his behavior. He used to be such a sweetie before others messed him up.
I hope Charlie works it out. Or, it sounds like his lifestyle is such that it's not a big deal.