If you've researched your car options and decided that the best car for you is a Honda Civic then your local Honda dealer becomes a de facto local monopoly on cars. The fact you could go and buy a different car somewhere else means that you have to choose to spend thousands of dollars on something that you know isn't the right choice. Dealers know this, and they're very good at making the most of it.

As you say though, the best way around the problem is simply to make sure you don't settle on a specific car so you're in a position to walk away if the dealer isn't great. That's easier to say than do though.