Here is a list of most common misconceptions about a dog's reactions that we, humans, perceive as abnormal (and label it as "reactivity":
- True dog aggression is very, very rare. In fact, 99% of the time your dog's behaviour is a learned bad habit, not a character trait. What I mean by "true dog aggression" is a behaviour when a dog wants to actually kill another dog, not just drive it away. If you have seen it, you would know.
- Barking and lunging is rarely a result of abuse or trauma. Yes, bad experience with another dog absolutely can affect your dog's behaviour, but it will only become a long-lasting problem if you allow it to.
- Petting the dog and talking to it will make things worse. Your affection and kindness are perceived as a reward for correct actions. It does not help your dog to cope; it confirms fears and reinforces undesirable reactions.
- Letting the dog "freeze" will 100% make things worse. By letting your dog stop and stare you are forcing it to make a decision about an approaching dog/human. Take the responsibility for making such a decision - treat an approaching distraction as if it was a nothing, and make the dog follow your directions.
- Asking a lunging and barking dog to "sit" without having means to actually make it happen will exacerbate your reactivity issues AND it will screw up your obedience. If you said "sit" the dog has to sit. If it didn't - make it. If you don't know how - don't say "sit." Otherwise, you are teaching your dog that listening to you is optional and that you words are just white noise, and you yourself are a nuisance that makes things even more stressful.
- Making a reactive dog to "focus" on you will not treat its issues. Avoidance and redirection are not a cure. They are absolutely useful and can work as a management strategy with dogs who easily redirect (a very minor percent of dogs by the way), but they treat nothing. Your dog has to make a conscious choice NOT to bark/lunge/cower and you need to learn how to get them to this point.
- Waving a treat in front of your dog's face will do absolutely nothing in a state of high arousal. It does not matter how valuable your treats are or how hungry you think your dog is. Mental arousal that high will always overpower food drive.
- Address undesired behaviour regardless of where and when it is happening. It should not matter who people around you are or what context there is. You let it slide once - you set yourself back for at least a few sessions.
- Playing tug will not make your dog more reactive or aggressive. I don't even know why this belief is so popular, it really shouldn't be. Playing tug is an awesome outlet for emotions, and a great way to bond with your dog. On a more complex level, playing tug or ball can actually be used to cure reactivity issues.
- Most important of all: get rid of that harness already. It is not gentle or humane. It is making your life a nightmare AND teaches your dog how exactly to use their legs so that they can pull you most effectively.