The phrase "took one side" implies a person's bias towards a particular party or opinion. Here are some antonyms for it, which depict impartiality, neutrality, and a balanced stance - "remained neutral," "stayed unbiased," "avoided favoritism," "maintained a fair outlook," "adopted a neutral position," "stayed unprejudiced," "had no particular leaning," "restrained from taking sides," etc. These words suggest the importance of not letting personal preferences influence one's decisions and behavior, especially when it comes to matters of public interest or social justice. So, instead of being partisan, it's better to be impartial and equitable.