"How does the "plank in your own eye" edict apply in situations where someone needs to hear the truth?"
Here is my answer:
My first question is rhetorical: "Who cares what you say if the intended audience doesn't hear it?" In other words, if they aren't listening, then our words make no impact. My feeling is that you have to earn the right to speak truth into someone's life.
Let me confess that this has backfired on me many times. I've sat down with a person in whom I've invested enormous time and energy, told them the truth about some area of their life that they needed to change or improve, and instead of receiving it well, I saw them accuse me of all kinds of malicious intent.
So, in the end, I have to ask myself this:
1) Have I really invested enough in them to feel I have the right to speak truth?
2) Is there any personal motive or malicious intent?
3) Is there any plank in my eye that I need to remove first?
4) Are they at a place where I can reasonably expect that they will hear my words?
If I can answer yes to 1 & 4 and No to 2 and 3, I should speak truth to that person.
And while there have been notable exceptions like I mentioned above, most people respond well if I apply the 4 questions above to the situation.