Personally I wouldn't tear them down.  But I don't own any of those homes.  I feel like it should be up to the owners of the homes to determine if they want to restore their homes, sell their homes or renovate their homes (including knocking them down and starting over).  What these designations do is change the rules after someone has bought which is unfair to the homeowner.  It's about holier than thou people in the neighborhood believe they know better how someone else should handle their property.  And what the people pushing these designation really want is to prevent any new development in the area, affordable or not.