Proper Tochachah: with Sensitivity

Rav Shmuel Huminer, zt”l, of Yerushalayim once noticed a very sincere ba’al teshuvah who was obviously proud of his long hair, which was then all the rage in the secular world. Rav Huminer offered to learn halacha with him so that he would know what to do. The two started a regular seder. When they got to the part that discusses that long hair is a chatzitza to tefilin, the young man was shocked. “My hair is a chatzitza?!” he exclaimed.
The next day he showed up to their seder with a short haircut.
One of Rav Huminer’s children asked him, “But why didn’t you just tell him that his hair is a chatzitza?”
The gadol answered, “I was afraid he would take it personally and be put off. When we learn it inside, it is clearly not personal and will not offend him.”
Of course, sometimes what is called for is to be strong. A well-known outreach Rabbi from Yerushalayim was once taking a walk with a fairly new student who sported a very long braid. During a pause in their heartfelt talk, the young man asked, “Rabbi, I get a lot of flak from people about my hair. But tell me the truth: what does Hashem really think of my hair?”
The Rabbi smiled and said, “Hashem? You really want to know what He thinks?”
“Yes, of course!”
The Rabbi shouted in a way that also conveyed humor, “He hates your hair! Cut off that braid!”
Fortunately, the Rabbi understood his talmid enough to know that the young man had merely been looking for a final push to adopt a more frum appearance! Caught once in a similar circumstance, Rav Huminer merely grabbed the young seeker by the sidelocks and cried joyfully, “Ah! Such beautiful peyos.” The young man understood on his own that the rest of it would have to go!