What's a polite way to shut someone down who is preaching to you about Jesus in public? I was working at a local farmer's market and this woman came up to me asking me if I prayed and believed in God and Jesus. I was there representing a university, not as a private person.
I would be tempted to say, "OH MY GOODNESS! Why on Earth would you ask me such a PERSONAL question? That's something I never discuss with ANYONE.". I would try to look as outraged as possible (which might not be all that difficult at that point in the discussion), and hope that the person gets discouraged and goes away.
It's happened to me more than a few times. I just hold up my hand in front of them at arms length (like stopping traffic) and tell them very firmly and very directly "I'm gonna stop you there". No one's ever persisted beyond that. P.S. I live in the bible belt.
I have a good way to shut them up if they will not take a hint. When they tell me that I need to have a close personal relationship with Jesus, I tell them that I am not gay or interested, but if he has an attractive smart sister, I might like to meet her.
Well my thoughts went out the window. My usual is Oh look at the time mom and I were going to skype. Or another one for me is oh your just in time I needed someone to help me finish my spell. That last one is a more extreme one but has been effective in ridding my doorstep of JW's. The first one is the one I use when having supper with my landlady if she gets preachy who is also a JW funny enough. However she is not pushy but she does get preachy when she is excited.
Now if you are running a booth you could just keep turning the conversation back to whatever the topic is. Or something to the effect of Excuse me mam I am here representing my school's blah blah blah I do not feel comfortable discussing religion as that is not why I am here. I would be happy to sell you some blah or discuss blah with you.
I would just politely tell her the truth. "I used to pray but soon discovered the line was dead." "Why Jesus? There are hundreds of religions being practiced today and hundreds more no longer being practiced. They all claim to be the right religion. They can't all be right."
I might end by bringing up the problem of theodicy: "If god is all-good and all-powerful, why doesn't god simply vanquish evil? Why does he allow innocent children to die horrible deaths due to earthquakes, tornadoes, and hurricanes, etc."
If she didn't walk away after that, then I would.