The Prohibitionist

 is a Stranger mission in Red Dead Redemption.

Story
A preacher, Abner Forsyth, is deterring citizens from the consumption of alcohol outside the player's home in Blackwater, upon speaking with him, he tells how the townsfolk aren't too fond of him. He proves it by sending Marston to one of his disgruntled listeners. The disgruntled man is a local bar owner, Oliver Phillips. He tells Marston that Forsyth is talking about the dangers and implications of drinking alcoholic beverages, and this has been causing the bar to lose business. The man then gives Marston a choice. Kill the preacher for money, or do not (if the player chooses not to kill the preacher, drinks throughout the entire world will be double cost).

Walkthrough
You can find Abner the preacher outside of the saloon in Blackwater. After speaking to him, he will tell you of certain people who are unhappy with his preaching. The player is then required to head to the disgruntled bar owner, who is near the dock of Blackwater. He says that the preacher is a menace to his bar keeping business and asks the player to kill the preacher. The player can choose to kill or not kill the man. If the player does kill him, he/she will receive $20 and half price at all bars across the map. If the player does not kill the preacher, a small amount of cash is still obtained but prices of drinks, homes, and rooms will double all across the world.

Tips

 * If the player wears the bandana, the player will not lose any honor but still attain a $20 bounty and still receive the perks. Make sure your bandana is put on before taking the shot and talking to the listener.
 * If you travel to the hill south of Blackwater, you can kill Abner with either the Carcano or Rolling Block rifle from afar, avoiding gaining a bounty of $20.
 * Using Throwing knives and a Bandana, climb up to the roof on the opposite side of the street and kill the Preacher from there to avoid the bounty.
 * The player must complete the Stranger mission The Wronged Woman before this mission becomes available.