When you arrive in Rodia, the Leather Jerks will stop you and demand bullets as payment to enter the town. You can go in guns blazing at this point to try and get rid of all of them, but there will be a lot of them to fight.
An easier way to get them out of town is to pay to enter the town and head to Dengler's house on the right. On the way, the maid will offer to lock in several of the Jerks so they can't join in when the fight starts.
Before attacking Dengler, talk to the Mayor in the center of town (you can talk to him in his cage from outside the area) and he will ask you to check on his son. Then, go to the Distillery (just north of Dengler) and talk your way in by saying you're looking to buy some of their product. You can find Chris Van Graas Jr. in the back, and he'll say he wants to take over the town by running out the Leather Jerks and killing his dad, the former Mayor.
Once you get into the office, open fire on Dengler and his cronies will instantly appear to fight you. If you take them all out, any remaining Leather Jerks will flee the town. Then, you can simply shoot the previous Mayor in his cage and go to talk to Chris, who will say he's taking over the town.