[Ollinson]

I was under the impression that this is what psychology/psychiatry is supposed to do by charter.

Most professionals I know in the field take the attitude that a patient's psychological state should only be corrected if that patient feels they are an impediment to their own goals. This also goes along with the popular alcoholics anonymous mantra "we can't help you till you want to help yourself" (I'm not advocating AA just that it's a popular approach).

Of course this doesn't apply to people who have behavior disorders or are violent and end up committed.

[foobar2020]

It is true that a mental patient can be forced to treatment only if (s)he is considered a serious danger to the society, or herself/himself (includes suicidal tendencies). In many jurisdictions a court's decision is necessary, usually obtained on a rather short notice (24-48 hours).

But this does not mean that patient's consent is required for a valid diagnosis of a mental disorder. Denial is a serious problem and somehow an internal part of certain diseases such as mania, or, as you mentioned, early stage addictions.