Faith Head
Someone who holds irrational religious fundamentalist beliefs and no matter what evidence is provided to the contrary will never change.
Bill: Hey George did you hear that geneticists have discovered the "gay" gene?
George: Bullshit, the devil makes them that way and it is my job to cleanse them of that evil!
Bill: George, you are such a faith head!
George: Bullshit, the devil makes them that way and it is my job to cleanse them of that evil!
Bill: George, you are such a faith head!