Very Good Points by all.
Add:
-Some folks just want to hear themselves talk.
-Some are looking for validation for their position
-Others just want to see if they can change folks, control folks, or agtitate folks.
-There are those just seeking attention - of any kind.
My best 'avoidance' of a religious agrument back when we had had some Moonies confronting folks in parking lots...
I was with a buddy of mine at the mall, here comes two representatives between two cars making a beeline...they asked their question..."what faith are you?'. I knew no matter what I replied, they had a programmed answer.
"I'm anti-athesist" I replied.
We continued on to my car, the two Moonies, staring at each other - stumped.
My buddy asked "where'd the hell you come up with that?"
I replied " I figured they had a programmed reply to any religion , agnostic, or atheist reply I gave - I just made that up on the fly".
I dunno , sometimes a smart-ass answer and walking off works - did that day, has since, hopefully will continue to.