"Deal with the validity of the time thing first. "
YOU: How about that?!! You're right! I am over the time allotted. I'll take a minute more to finish up and then give the floor to the next person. And , Rickles, in the future if you have something to tell me like this, you don't have to be sarcastic! Just raise your hand to be acknowledged. As I was saying....
R&R: Whenever a Tank is right, it is prudent to admit it in one brief sentence and then head for the future. When you said you will take a minute more to finish up, that was a signal that you are heading for the future. Now that you've dealt with the validity of his grievance, there is nothing left for him to hide behind and you can point out the inappropriate Sniping behavior. Once again, because of your calm and professional handling of the situation, you have isolated the Sniper.