I believe this kind of hostility is unnecessary. FSBO sellers and agents can work together. Indeed, they should work together. What a FSBO seller does is basically the job of a listing agent. Will a listing agent make enemy with a buying agent? After all, if somebody manages to find a buyer, he should receive some commission as his pay.
A buying agent should not get hostile with a FSBO seller either. He is just another agent representing his client, who happens to be the same person. Will a buyer agent make enemy with another agent selling his own investment property?
If you decide to go the FSBO way, be ready to receive a lot of calls from the agents. Don't hang up right away. Make friends with them! I have received about 20 to 30 calls altogether during my 4-week period of selling my house.
All these agents will try to lure you into signing a listing contract with them. Don't! One agent told me that they have a 'special' package for private sale owners. After asking him for more clarification, it turned out to be just another package for listing your home with them.
Here is the correct way to handle an agent. First of all, tell them that you will not be listing your house with them for now, but you might need them in the future if you fail to sell it privately. You simply don't want to burn your bridges.
Then tell them that meanwhile, if they happen to have some potential buyers (some might bluff that they do already), bring them to you and you will be willing to pay them commission. They might have a rate in mind. Tell them upfront the commission you are willing to pay. If they turn out to have some real potential buyer, sign a contract with them only for that potential buyer, or in some case, a 24 or 48-hour listing contract.
I still remember about 2 years ago, I was curious about the market price of my house, but I was not ready to sell it. I called up an agent, and he insisted that he needed to take a look at my house before he could tell me a price. He came in, looked around, and said he happened to have somebody looking for a house like mine. Then he pulled up a listing contract and wanted me to sign a binding agreement with him for 120 days! Of course, I refused.
Knowing that you are not interested in signing a listing contract with them, some agent would want to hang up. Don't let them go so easily. Get to know them more. Ask them about their experience in the industry and what they think about the current housing market. You are going to get a lot of insight from them. Try to build a relationship with them, for you never know when you will need them in the future. You may be surprised how many of them would like to continue the conversation. Some might even be willing to evaluate your asking price and analyze other houses for sale in your area.
Agents are your friends. Don't make enemy with any of them. Even the agents themselves know about this truth. Look at how they swap business cards around, knowing that they are all competitors of each other in some sense.