Labeling an adversary as "insane" or "crazy" is a convenient and commonly used way to shut down any discussion or inquiry into the grievances of that person, lest they reveal an underlying problem which we don't want to address.
The interesting split is to see when something is called "ideologically" driven versus something merely painted as the act of a "crazed" person.
Indeed. It's interesting to see how people's framing of a topic sometimes communicates more than an answer to direct questioning could. This calls to mind another split where wealth is the cushion: When the poor are deemed crazy but the rich merely eccentric for perpetuating similar, negatively perceived actions.