Presumed opinion on an object of inquiry obviously yields a prejudiced subjective result tinted by personal bias. Because of the vested presumptuous interest, being objective becomes an issue.
This will eventually lead to casual relapse into ignorance, constantly neglecting what is obvious because simple curiosity has been replaced with fixed assumptions. This is more explicit in religion, family affairs, abusive relationships, fandoms, sports, etc.
You observe that the emotional attachment and familial bonds formed in the above social groups usually end up creating blind-spots and too many self righteous hypocrites.
Having presumptuous interests before an inquiry may end up spoiling the broth. Neutrality is the keyword for absolute objectivity or else the inquiry is already soiled and subjective – tainted!