Cesar Millan talks extensively about the power of the pack; the ability for the pack to do what humans cannot, no matter how smart or loving we are. Sometimes we have to let the pack do the work they are intended to do...
A balanced pack can bring an unbalanced dog into their folds very quickly, with a few exceptions. One is where the pack recognizes a truly bad energy from the new member and decides that is not for them. They will usually walk away from the unbalanced energy and extend no invitations to play or to roam with the pack. This means their is some work to do from the pack leader with balancing whatever the issue is with the individual dog.
A second exception is where the new dog is not aggressive, but fearful/dominant and that affects their ability to walk with the pack. Kobe was one such dog. A Havanese, he would act dominant until he got around the rest of the pack then he would distance himself while acting as though he was the leader. The pack would walk away from him which he was constantly confused about.
Eventually, both Koa and Mc would "bat" at his butt, something I had not seen either dog do to any other dog... and while Remy (calm/submissive) was right next to him on the walk, they would only do that to Kobe. In fact, whenever he would fall behind, they would go back to him and start prodding him along physically.
I eventually realized that this was something humans do in a different way when we want someone to either play or "get in the game". When I came to this realization I stopped controlling the intensity of the prodding and Kobe started not only playing but inviting others to play. Granted it took 2 weeks, but the pack accomplished what humans cannot because we read things differently and handle things in a less primal way.