Why isn't psychotherapy more direct with patients? While it is possible to  tell someone that they are affected by OCD or they are narcissistic, I think that trying to help people simply by giving them direct advice doesn't work. I also think that citing authoritative sources, which show that they are positive to some disorder diagnostic test, usually doesn't work.

Dale Carnegie explains that people don't take into consideration what is right or the truth, but what doesn't hurt their self-esteem.


Can you explain me better why psychotherapy is not directly telling patients what their diagnosis is? 
Why is it more effective to avoid being direct in trying to correct people's personality traits?
Is this phenomenon bound to confirmation bias?
One therapeutic issue with being confrontational – a problem that does not arise unless one is direct in a bad way – is reactance. I've described this issue in a separate answer to a question you commented on five days ago, "How to change someone&#39;s beliefs?" Telling someone who doesn't believe he or she has a problem that s/he does have a problem implies that s/he should change. If the person is inclined to deny the premise of this implied suggestion, the person may also resent the suggestion itself. Thus resistance and defensiveness may arise in reaction to the suggestion that s/he is not free to simply continue behaving "normally" without further consequence.

Another potential problem with directness in a bad way  may arise by carelessly assigning diagnoses. Diagnosis of psychopathology is a very difficult process; despite my PhD, I am not qualified to perform it. Even those who are qualified (officially, at least) do not perform it with satisfactory accuracy by my (high) standards. Part of the problem is directness in the context of careless inattention or inexperience (see also schema modification). I.e., directness is not the real problem here, but it provides a channel for these problems to cause other problems via communication of misinformation, especially in the context of professional authority. Non- psychologists tend to defer to the authority of psychologists even on topics beyond the expertise of both parties. This makes restraint on the part of the more authoritative party very important. Failure to withhold first impressions and unexamined opinions about possible diagnoses can result in psychologically harmful labeling. This can impose anxiety-exacerbating pathological characteristics on the identity of the person so labeled, especially if s/he does not possess the wherewithal to question these labels or is predisposed toward anxiety or self-loathing, as often apply to psychotherapy patients.

In the opposite contexts of psychotherapy that is not pejorative or otherwise invalidating (e.g., Rogerian and other humanistic modalities) practiced by therapists with appropriate restraint and excellent breadth of experience, directness is probably desirable and helpful. Methods such as motivational interviewing benefit from their direct focus on clients' own ambivalence toward positive changes, which is often the root problem, especially with ego-syntonic disorders. Conversely, ego-dystonic disorders may benefit from treatment via methods such as cognitive behavioral therapy that directly address problematic, derogatory aspects of clients' identities, such as the inflexible conviction: "Something is wrong with me." Thus directness itself is not the problem, but more a moderator of the consequentiality of a therapist's choice of approach to the problem a client presents. If the approach chosen is bad, harm may be reduced by self-restraint. If the approach is good, benefit may be enhanced by directness.