my dog used to be fine with humans and other dogs. but now, he always barks up a tantrum everytime someone is in view (and i mean, this can be 15 feet away and he'd be barking.) so today, i took him out to relieve himself, and my neighbor walks out, and my dog totally just goes crazy, pulling himself free from the leesh. and this just wasn't acceptable. but i really don't know how to free him from this problem. any advice?