Looks like you've been solidly answered by Kdude and Southern Kross, Athenian. Can't speak for everyone else but when Fi manifests, right and wrong become crystal clear. Whether it's everyone else's perception of right and wrong is debatable.
To provide some concrete examples of Fe gone wild, refer to Salem, the attempted genocide of Jews, the treatment of heretics all over Europe, the attempted genocides in Bosnia and Somalia and the Crusades. Also, discrimination as it relates to gender, race or sexual preference.
There are no bullet-proof checks and balances to either Fe or Fi. We can only rely on an individual's moral compass.