Truth be told, I associate Fe with PC mongering lunacy/idiocy. (Sorry, I do).
That is pretty close. Being politically correct means being sensitive to other's differences whether they be cultural, religious, ethnic, etc. And sensitivity is reacting appropriately to the emotions or situations of other people. When done verbally, this is known as tact. Sensitivity and tact are fundamental tenets of Fe.
As Bluewing said, Fe focuses on making society better, whereas Fi is related to just making it's user happy. Fe users want others to accept their values, so society can be a better place for everyone whereas Fi users could care less what others think of their values because their values only serve to make them happy.
Personally, I associate Fi with closeminded and needless attacking of differences which translates into lunacy/idiocy.
Just as Fe can be associated with being overly PC, Fi is associated with bigotry. So Fe users will usually find Fi users to be intolerant and prejudiced and Fi users will find Fe users to be imposing and coercive. Transcending the Fi/Fe barrier is something I've noticed that even the most intelligent posters have little success with doing. As a result, most debate threads end up with the NTPs and NFJs against the NTJs and NFPs. It's one of the most recognizable patterns on this forum.
In simple terms, it is a battle between the value constructs of tolerance (Fe) and morality (Fi). Taken to the extreme, tolerance can be seen as inherently immoral by Fi users, and morality can be seen as inherently intolerant by Fe users.