"Deactivate Barrier" is an objective in the story mission Where Angels Fear to Tread.
With Claptrap leading the way, just follow him over to the red barrier, the Competitor Deterrence Field. Do not cross through it as it will instantly kill you. Wait for Claptrap to remember you are not a robot so he will open the security gate and let you on through.
Claptrap: "Minion! I've started my attack! I'm going to tag every inch of this mountain if it's the last thing I do. Let's go!"
Claptrap: "We're gonna make Jack regret ever setting up shop on this cliff! it'll take him minutes to wash this graffiti off! MINUTES, I SAY! HAHAHAHAHA!"
Claptrap: "Are you comin' or not?"
Claptrap: "Oh. Right. You're not a Hyperion Robot. I forget that sometimes."