The truth hurts--it really does. When we receive criticism or correction it causes us to flinch... especially when it comes from someone who is important to us. Certainly, everyone has experienced the sting of the truth and the resulting hurt feelings. When people are hurt, they can become defensive and put up walls to defend themselves. They feel like their very beings are being assaulted, and they can respond agressively toward the person hurting them and fight back.
So, as much as possible, most people avoid confronting each other with the truth. They avoid confrontation because they think that this is the best way not to harm the relationship. However, when there is friction between people, the irritations lead to sores which go on to fester--eventually causing so much pain that people separate from one another in order to find relief.
Some irritations are trivial and are to be expected as people interact, so it just isn't reasonable to confront every little thing. But when those we love have life-controlling problems, the damage that occurs is not trivial. Confrontation is necessary because the loved ones are damaging themselves and those who love them. Life-experience tells us that when we confront someone with the truth we risk being hurt.