It's possible, but not impressive. At least not the gameplay you linked. The guy has the Predator/Reaper/Pavelow set-up, specifically designed for kill whoring. He capped the B Flag, and then camped out under it the ENTIRE match with a motion sensor.
Things like that, I really don't consider legit, and find it pointless to upload them to Youtube. It takes little skill to do. These "high kill" games like this stopped being impressive after MW2 when everyone started using Kill Streaks for most of their kills, and camped out in one spot for most of the match.