"Nice" people lie constantly because they are too cowardly to say what is true. It is possible to be honest & to be kind about it, but it is impossible to control how someone will react, and how someone reacts is their responsibility, not yours. Having proper personal boundaries means understanding that the truth will inevitably offend someone. But the only sustainable way for people to relate to each other is through reality. I think this is what is meant by "God must be the center of every relationship." People who deal in truth & reality can resolve conflicts, those who do not can never have any real common ground—they are lost in a realm of delusion, & will be plagued by arbitrary whims & unresolvable paranoia.