The phrase "be one side" denotes a state of being partial or biased towards a particular viewpoint or opinion. Its antonyms, on the other hand, suggest a neutral or unbiased stance. One antonym is "be impartial," which means to remain fair and just while appraising a situation, without exhibiting any sort of personal prejudice or preference. Another antonym is "be equitable," which denotes a balanced and unbiased approach towards all parties involved, in order to ensure justice and fairness. Other antonyms for "be one side" include "be objective," "be even-handed," "be neutral," and "be dispassionate." All of these words aim to counteract partiality and promote fairness and impartiality in all settings.