When I started out as a Realtor (was in 10 years before leaping to financial planning), I did drive clients around to rentals because those were the small potatoes more established agents in our brokerage didn't want. Most of my peers would not take a client to a FRBO property that didn't guarantee a fee (either listing a flat fee or saying something like "brokers protected"). After all, who wants to spend days on a client and not get paid? For the same reason, until the market crashed, they wouldn't take clients to see properties with low commissions either.
I think the agent was right to ask if you would pay them for the reasons someone else mentioned above (time spent with the client which helps the client understand what's available and what they like, probably will still help them review paperwork, and plus the agent can make the decision whether or not to help their client if anything else arises with your property/paperwork). It's so much better to ask up front so everyone's clear. That said, you have absolutely NO obligation to pay him.
A fun fact: you'd be AMAZED by the amount of seller-buyer collusion of trying to say they discovered each other on their own so that all can save on Realtor fees. In your case it's the truth, but the problem was so bad that our agency agreements with the client (buyer or seller) we stipulated they would pay commission on anything they buy during the agency agreement. I hated those clauses when I was a military spouse moving every 2 years. Then I became a Realtor and discovered why they're in the agreement!
I still took clients to see FRBOs and FSBOs because I wanted to provide the best customer service (unfortunately poor strategy), and also because I hoped to convert the FRBO or FSBO into one of my listings (very successful with this). So if you don't need an agent to help rent out the property, then great. But if your interest dies down, you might consider establishing a brokers fee.
Also, sometimes it's better to get along, sometimes even pay to play, especially if this is your first rental. A good agent does more than just advertise (or, in your case, walk them through the process with a higher comfort level since he didn't bring them to you). And even if you don't like that particular individual, there could be some benefits in playing nice with his brokerage. There can also be some downsides to being perceived as rude (not saying you were) depending on how rural the area and which brokers are strong there. Especially since this is winter- a tough time for rentals in any area (let alone a rural area) and your first deal where you'll go through the process of vetting the applicants. Not saying you 100% need a broker to run a background and credit check (you don't). Just saying it's your first deal and you don't know what you don't know. BP forms are some of the best I've seen as far as stock forms go, but they can't possibly cover all the "gotchas" of a local community that a good broker can help with.
So while I'm not saying you should have worked with this guy, I am asking you to step back and realize he's not necessarily a jerk for asking if you'll pay him. I feel like I'm rambling so I'll stop now. I hope that helps some and that your first deal goes amazingly well!