Hahaha!

I lived in LA for a while, and there's a chruch that preys on homeless by helping them out and then brainwashing them to zealously promote the church.

It really confuses brainwashed folks when you bring up facets of thier religion's history they don't know...

Like reincarnation was a doctrine of the catholic church until the 2nd committee of Constantinople.

"but I'm not Catholic, I'm Christian!" they'd say.

Until the reformation in the 16th-17th century, there was no difference. The Catholics held all documents related to the religion in Latin, which most common folks couldn't read, and translated the same texts later for public consumption.
What bible do you use?

(usually King James)

Oh, the version that King James re-wrote to allow him a divorce, which was forbidden before. Right.

It says in the bible that if a man so much as changes the style of a letter of a word, that the text is to be considered invalid (loose translation, not exact quote)

What is a translation?

If it's truly God's word to be taken literally,
have you read the original Latin or Greek versions?

(by this point they're in over their heads and realize it)

I love comparitave religions. Did you know that the story of Noah and the flood predated the bible in Sumerian and Babylonian texts (both areas are prone to seasonal flooding)
exact to the types of birds released?

Needless to say, this is a long way to go.

A friend of mine had another approach:
Invite them in.
Let them speak.
Pay attention to the start and end time.
Thank them for sharing their beliefs and ask the same of them,
quoting the time he'd spent listening to their opinion.
The will usually be uncertain, but agree if you've been courteous.

Then he's open with:
"I'm a witch. I follw the traditions of pre-Christian religions of my European ancestors before me..."

They forgot their bible on the dash for the door...
Two minutes return for a half hour investment of time,
but they never came back...