Want to make a christian angry?
Tell them you find their mythology fascinating.
Ask them if they believe in extra terrestrials - most answer no - then why do you believe in a god, angels etc who live 'up above' - that defines an extra terrestrial
You say that, but I had a friend in high school who once told me that he figured angels and aliens were actually the same thing...
@GregM I too believe that in the past, maybe distant past and up to present, alien civilisation(s) have visited and probably interbred at some stage ... too many mythologies and legends in too many cultures of gods flying through the sky, flaming chariots in the sky giants roaming the earth, etc
"Aren't you a bit grown up to keep on believing in fairy tales?!"
"I chose rational thought, not magical beliefs," I tell Christians.
This shuts them up. Perfect.
I find pentagrams work well. Scares AND angers them.