Free the slaves in the slave pen, for the Rangers.

Free the slaves in the slave pen, for the Rangers is a quest in Fallout 2 obtained from Elise, the head of the Rangers in NCR. By doing this quest you're aligning yourself with the Rangers and, respectively, you can not do it if you have the Slaver Reputation obtained from Metzger.

Walkthrough
After agreeing to become affiliated with the Rangers, Elise will direct you to free the slaves in the Bazaar area of NCR. The area is guarded by a gang of slavers so violence will be an inevitable necessity for the completion of this quest.

To free the slaves, you must use the terminals on each of the pens. Sometimes the terminals won't respond on the first interaction, so keep trying.

After returning to Elise, you will receive 3000 XP, a Ranger Pin and be officially regarded as a ranger. This does not give any unique quest possibilities further in the game, but will affect how some non-player characters react to you. NCR Ranger patrols found in random encounters will recognize you as a fellow Ranger and greet you as friendly, but slaver caravans are much more likely to be hostile towards you. Sheriff Marion in Redding will also recognize you as a Ranger, unlocking some additional dialogue options with him and making him accept you more quickly.

You will be unable to receive any of the quest rewards if you free the slaves prior to speaking to Elise and accepting the quest.

Alternate routes

 * There is also a way to free the slaves without resorting to violence, though this requires exploiting the game combat mechanics in combat. You can flee from a combat by just walking to another area. If you initiate combat with one of the slaver guards they will all come after you. When they do, simply walk back to the city with the men after you and once you enter the city, the men will stop near the entrance. After this, you may simply sneak back to the slaver compound and free the slaves without killing a soul.
 * As long as you are not seen by the patrolling guard, you can simply open each gate in turn until all the slaves are free and simply walk out.

Bugs
Keeping the entire slave compound on the screen can result in game slowdown, making unlocking the gates even more tedious without the proper skills, or if your companions are lagging far behind.