An empathic person has a lot of daily hurdles to overcome in today's disconnected and disingenuous society. Their heightened ability to feel as others do leads them to to struggle with the underlying feelings that most people ignore but still project.
Even if they can't feel exactly what is underneath the mask they know when a person is feeding them nonsense. This drives empaths crazy, as they understand what monstrous elements lie in wait in everyone.
That isn't to say that everyone that 'wears a mask' is hiding a terrible or damaging personality, some hide their pain as a way to protect those around them. Regardless of the reason, empaths pick up on those hidden agendas and feelings. They are never positive, and the fact that the person is trying so hard to avoid their problems instead of deal with them confuses any empath.
There are innumerable reasons that a person may choose to project a false persona. Some do it to gain acceptance, others to hide their pain, even more do it because they don't understand how they feel or what to do about it. An empathic person usually reacts the same to these people.
The natural reaction is to avoid this person. The feelings of confusion and discomfort that occur around and from this person are felt on a near physical level for any empath. This method of aversion gets tricky when you actually like the person and want to help. When you aren't up to helping that person, it can be hard to deal with the guilt of avoiding them.
You have to look out for yourself. Plain and simple. Running yourself ragged emotionally to bring a horse to water doesn't ensure that it will drink.
Don't be afraid to say no when you need time to deal with your life or simply recuperate. Don't let their confusion become your confusion.