Faith is not real without repentance [emphasis mine], and faith is not like that of the demons, simply assenting to truth claims. Faith works itself out in love. Faith follows after the lordship of King Jesus. Faith takes up a cross.
Imposters appear everywhere, churches, organizations, companies, families. They are most destructive in the family environment, which includes the church. When motives are purely selfish and the goal is the management of an image to obtain their desires, beware. There are telltale signs– I recommend this article that explains them: http://psyed.org/r/cog/bw/bwd/manip.html. The article focuses on “abuse”, but don’t let that term confuse you. What a manipulative person is doing is a form of abuse. Works by Dr. George Simon are also very helpful. You can find some of his online works below:
We are to be “innocent as a dove, but smart as serpents” (my paraphrase). Another words, we are to be wise to the ways of world, to know and understand that evil exists and how it operates, yet we are to remain pure and holy and not participate in the evil, but flee it, pray against it, and honor truth and light wherever we are.