The Borg assimilate individuals and their entire mind becomes a part of their collective. Every time they to do this, they must gain the exact experiences and legitimate reasonings as to why other lifeforms do NOT want to be a part of the collective.
The Borg must completely understand an individual's perspective. Where in any of the Star Trek series, is there an explanation as to why they continue to assimilate and disregard the individual's reasoning? There must be a reason(s) that the collective has that overrides any individual's feelings/emotions, reasons, and value of free thought.