Or "should not" change their mind. If I hard disagree, then I should not change my mind, because I see no valid reason, and both my experience and reasoning are solid to the degree I am certain the arguments presented can not develop into a valid reason to change my mind. "Hard disagree" may signify being certain. I then am responsible, for my own sake and wellbeing, of being right in relation to reality, or reality will simply hard disagree.