The priest was considered a schismatic for advocating the division of the church.

schismatic 是由名词 schism（分裂、分立）加上后缀 -atic 构成的形容词，表示"分裂的、分立主义的"。作为名词时指"分裂主义者"，特指在宗教团体中主张分裂的人。