I disagree with Resonance's assertion that Fe should not be expected to be taken as an indication of one's internal state.
When one professes an opinion, are they not professing the content of their internal state?
What is Fe? It is the outward expression of an opinion (sweet talking, as in INTPNess's example, conveying he feels fine about people showing up late when he's really mad about them doing so, etc). I understand that Fe's purpose or intention/motivation/whatever is social harmony... but to say people should understand that what opinion they are professing is NOT HOW THEY ACTUALLY FEEL THEMSELVES, EVER [and can even run completely opposite(?!)]? Nonsense.
In this way, Fe, because it is NOT a reflection of one's inner state, -when it professes to be- (<- key), is fake.
But I'm not saying only Fe is fake. Any human can be fake. And being fake is furthermore just a fact of life, that is not always bad. Just defining the action of professing an opinion that you do not actually hold as "fakeness." I contend Fe is fake if you define Fe as "espousing an opinion [or stance] designed to promote social harmony even when your internal opinion [or stance] on something may be contradictory"... which is what seems to be what is being said (may be misunderstanding, disregard and sorry if so).
Disclaimer: I don't hate Fe. Also, my use of "is" and "can be" is a bit mixed in this post. I don't mean Fe is always fake, but I don't feel like figuring the proper wording to make "can be" work in the relevant sentences.