An easy way to pull this off is with Bot Bootcamp. You have to basically cancel a capture of a control point by an enemy. (The Control point will have a partial ring around it of the opponant's team colour which goes away when you enter it).
In Bot bootcamp, you don't even have to kill the enemies, pick and camp a control point somewhere in one of the levels, let the AI run in and start the cap. If you fire at him enough to pop shields, he'll backpedal out of the control area and retreat until his shields come back. That's your first secure. He'll run back in when his shields go back up, either pop them again or smoke the bot.
you should be able to get your achievement before you hit the halfway mark of a match. The key is to not kill the bots every time they start capping, just chase them out of the control point long enough for you to turn it solid to your team's colour again.
Out of all the maps, i found it easiest to pull this off on Control point C on Recharge. Hide behind the crates or the big cylindrical machine, the bots will tend to run in from the open are entry instead of the stairs, as long as they don't see you they'll run right to the control point.