Problem is he doesn't have to actually bite someone for them to report him as being out of control and this could even result in a destruction order. You MUST keep him under close control when there are people or dogs about. Keep him on a short lead, or use a flexi lead in the park. Only let him off when you are sure there is no-one else about, or until you have trained him to drop on command or return to you immediately. When walking near people make him sit or down and wait till they have gone past. As for a muzzle it doesn't matter what other people think provided you know he is safe. You could also try a Halti, which gives you more control of his head.