no you cannot. you cannot CONSISTANTLY be at the top of the score board killing people afk.
if it is the difference between 2 to 3 kills, then it killing people afk is a skill and a valuable tool. its a free point and whoever can take those opportunities most effectively wins. but really, how many times do you ever get a chance to kill someone afk? maybe 2 or 3 times at most in a 20 minute match. less if its based off of kills.
the fact of the matter is, there are not alot of games where people just stand around afk for long periods of time. they are usually afk for a minute or two, and if they had sense, they type afk. with the new patch, (with the one of two things they did right, the other being eax support) you get that cute little box over your head for config. AND if they had sense, they would go to an out of the way location to do what they needed, away from the fray.
If killing afk'ers is the difference between 2 or 3 points to win, then it becomes a skill.
People consistantly at the top dont cannot rely on afk kills to put them there.