I have to agree with some of the previous comments. As new creations in Christ, our minds and desires have been transformed, and we have crucified our flesh, but as long as we live in the body the flesh will still be present.. We have the power to control it, but it's still there. I believe that due to the flesh we still can't enjoy a perfect relationship with our brothers and sister in Christ, or at least not for a long period of time. There are also the wolfs in sheep clothing that will sneak in.
Many of us carry deep scares from the days living in the flesh that will go away only in Heaven, so when we talk about a better relationship with fellow believers, I look forward to the Kingdom to come.