argue, reason - present reasons and arguments

apologise, rationalize, apologize, rationalise, justify, excuse - defend, explain, clear away, or make excuses for by reasoning; "rationalize the child's seemingly crazy behavior"; "he rationalized his lack of success"

stick up, stand up - defend against attack or criticism; "He stood up for his friend"; "She stuck up for the teacher who was accused of harassing the student"

uphold - stand up for; stick up for; of causes, principles, or ideals