By making one feel that something needs to be changed about them, and that they're not loved just the way they are, it can completely hault any spiritual progress they have made, and maybe even go backwards.
By loving them exactly the way they are, not trying to change them, they feel the loving and supporting space you hold, and thus the changes in their highest alignment will naturally occur.
Of course, if there is a factor that needs to be expressed because it has not respected boundaries, then that too can be expressed in a diplomatic and loving way, not projecting, but by simply stating your personal experience out of love for yourself.