I do strongly advocate buying local, but I don't think it's always the customer's fault. Just because a sign shop is just around the corner, doesn't mean that it should automatically get all the local business.
What happens when you Google "Signs in [insert town name here]" do you come up to the top? If one of your out of state competitors do, then that's not the customer's fault if they pick someone else. How about Yahoo? The phone book? In their mailbox?
This is true with every business, but especially true with politicians. When they register to be on the ballot, they immediately go on a list. That list is picked up by dozens retail political sign printers, many out of state. They'll call, email and send catalogs to gain top of mind awareness right out of the gate. Then when the politician has raised his money, he already has someone in mind.
And yes, townships using local tax dollars to buy anything out of town that is manufactured locally frustrates me too, but the buyers are only human. They don't know every business in town, and they have strict budgets to work within.
I'm only saying this because I run my business this way. Instead of making a customer out to be evil because they don't buy from you, ask yourself why. Why did I lose that sale? Why did they order signs from 450 miles away. Why didn't they even call for a quote? I'll bet dollars to dimes that if you called that politician, or the city of Montgomery and asked them why, they would tell you they either didn't know you offered that kind of product, or that they did call, and someone out of state with a different set of strengths and efficiencies beat your price, and possibly service/speed by a margin that was important to them and those they answer to.
I don't want to pick a fight, but business is earned by those who go out and look for it.
P.S. I understand there are jerks out there that can't be worked with, and this guy might be one of those. If that's the case, why would it bother you at all that you didn't have to work with him. Good riddance I would say.