I sure hope this wasn't your first and only Meeting you have been too. . . wouldn't want this type of behavior to keep you from going to other Meetings.
I hate to say it, but just about everywhere you go, unfortunately there are the insecure people like that who, instead of focusing on themselves, have to try to knock others down to make themselves feel more secure. I'd just make mental note to stay away from these people in the future.
I am not in anyway knocking NA Meetings, so please, don't think that I am, but I have always felt more comfortable at AA Meetings in my area. I have went to several different NA Meetings and have found at the AA Meetings in the Dayton area, people tend to be more compassionate, friendlier, have more members with a longer term of Sobriety . . . I just felt more welcome all around.
As far as saying anything to anyone, I'd try a different Meeting (a different day and/or time,even if it is at the same location) and if these same people are there and it happens again, maybe you could mention how it makes you feel to the Chairperson of the Meeting afterwards. Let him/her know that you are a newcomer to the Meeting and how uncomfortable it made you feel. You will not be put on frontstreet, but I imagine the Chairperson will bring this up at the next Meeting as a group conscious. Behaviors like this need to be brought to people's attention so it hopefully will make others think before openly bashing someone else.
Glad you're trying Meetings, willing to go to any length, remember?
God Bless,
Judy