How to know if you're dealing with an ideologue

I would define an ideologue as who someone blindly rejects every idea from the other side of the aisle in favor of their own uninformed view. You don't have to accept everything that purported experts say to not be an ideologue. You do, however, have to be informed about what the views are. Identifying an ideologue then become a simple matter; those who refuse to even consider what one's opponent says are ideologues (if you don't consider it, how are you to know it should be rejected?). Those who are conscientious in their rejection of a given view (i.e. those who have thought about the matter) are not.