Turns out, I don't have to go inside the building to feel agitated by being there. I spent about five minutes in the parking lot, spoke to only one person and that conversation was pretty innocuous.
Afterward I felt wound up and agitated, like I'd had three too many cups of coffee. If I'd sat still and thought about it I would have cried.
I expect this. I understand that I have a conditioned fight/flight response to this church. An acquaintance put it succinctly: "Even people who don't believe in God believe in B.F. Skinner."
I understand it and I hate it.