I usually just go about my business and try to ignore them. After a few minutes of them provoking me with no response, most people will just quit or find someone new to bug. I've found this invaluable for dealing with the spawn-killers in Red Dead Redemption.
I don't care about my online record/stats though; I play for fun or Achievements. Not sure what you could try if you were aiming to preserve a specific win/loss ratio.