FINDING THE TRUTH

The first basic, before any argument should begin, is to agree on the definitions and on the parameters of the argument. If a person does not understand objective versus subjective information, you cannot argue with them, especially when they want to use subjective information as objective information.
Objective Evidence is physical evidence that someone, when reviewing a statement, can inspect and evaluate for themselves. It provides compelling evidence that the statement actually represents the information which can be proven true, based on facts that substantiate the charge being made. The evidence must not be circumstantial but must be obtained through observation, measurement, test or other means. Another words, can we have the evidence this person is using to make this statement please?
Objective information is to subjective information as "matters of fact" is to "matters of taste." You can only really argue about matters of fact. Matters of taste are "subjective" in the proper sense of that term ("I like ice cream," "I think classical music is for the birds").
SUBJECTIVE EVIDENCE is evidence that you cannot evaluate -- you have to simply accept what the person says or reject it. Subjectivity basically is a ‘personal opinion’ which can also be considered as ‘personal feeling’ or ‘personal conclusion’ which is based on ‘personal information’. Self-deception is the process or fact of misleading ourselves to accept as true or valid what is false or invalid. Self-deception, in short, is a way we justify false beliefs to ourselves. Believing in something false doesn't make it true! If I believe I can fly and I jump out a window, I'm still gonna fall.
When philosophers and psychologists discuss self-deception, they usually focus on unconscious motivations and intentions. They also usually consider self-deception as a bad thing, something to guard against. To explain how self-deception works, they focus on self-interest, prejudice, desire, insecurity, and other psychological factors unconsciously affecting in a negative way the will to believe. A common example would be that of a parent who believes his child is telling the truth even though the objective evidence strongly supports the claim that the child is lying. The parent, it is said, deceives him or herself into believing the child because the parent desires that the child tell the truth. A belief so motivated is usually considered more flawed than one due to lack of ability to evaluate evidence properly. The former is considered to be a kind of moral flaw, a kind of dishonesty, and irrational. The latter is considered to be a matter of fate: some people are just not gifted enough to make proper inferences from the data of perception and experience.
However, it is possible that the parent in the above example believes the child because he or she has intimate and extensive experience with the child but not with the child's accusers. The parent may be unaffected by unconscious desires and be reasoning on the basis of what he or she knows about the child but does not know about the others involved. The parent may have very good reasons for trusting the child and not trusting the accusers. In short, an apparent act of self-deception may be explicable in purely cognitive terms without any reference to unconscious motivations or irrationality. The self-deception may be neither a moral nor an intellectual flaw. It may be the inevitable existential outcome of a basically honest and intelligent person who has extremely good knowledge of his or her child, knows that things are not always as they appear to be, has little or no knowledge of the child's accusers, and thus has not sufficient reason for doubting the child. It may be the case that an independent party could examine the situation and agree that the evidence is overwhelming that the child is lying, but if he or she were wrong we would say that he or she was mistaken, not self-deceived. We consider the parent to be self-deceived because we assume that he or she is not simply mistaken, but is being irrational. How can we be sure? I will allow some slack to the accuser.
OBJECTIVE EVIDENCE is evidence you can examine and evaluate for yourself.
In the case of objectivity, we have an external and independent ‘object’, which can ‘verify’ the truth-value of the objective information or statement. In the case of ’subjectivity’, the contents of personal information, on which the subjective opinion was based, were known only to the person who held that subjective opinion whereas in the case of objectivity, the ‘external object’ (or event) on which the objective information is based, can be known to everyone whoever himself wants to verify the objective statement. In the case of an objective statement, there is an underlying assumption about the existence of some ‘external object’ that can verify the truth-value of that objective statement and vice versa that in a false objective statement there is a lack of any ‘external objects’ to verify the statement. Whoever is interested in knowing the truth-value of an objective statement, can resort to that ‘external object’ or the lack of any ‘external objects’ for this purpose.