The stats are a good incentive to play more. It encourages people to get into the top 100, or the top 10 or the number one spot
Thus, they play more, kill more.
Killing more people helps the team. (loosing equipment, loosing men at strategic positions etc)
So overall, stats help keep the server full and the team progressing.
Although i completly understand that there are people who take the stats far too seriously, F4'ing like you said. Going off on their own when they are needed the most on another place etc.
But most of the time there are admins online to watch out for such anti-social immoral behaviour.
Overall, as long as the "stat whores" keep on killing, i have no problem.
More dead marines/aliens = better for the team.