Neutralism, as a concept or philosophy, refers to the act of taking an unbiased or neutral stance, without taking sides or showing any preference. However, there are certain antonyms to neutralism, which mean the opposite of it. These include partialism or favoritism, which refer to the act of showing prejudice or favor towards a particular person, group or idea. Also, one can use words like biasness or partisanship, meaning the inclination towards one side or the other, regardless of the facts or evidence. Another relevant antonym is polarization or extremism, which suggest a strong adherence towards one side, resulting in the dismissal of alternative views or opinions.