It's a shame that the guy said this but i can understand it...
I did a 4 week stint in rehab in Spain and on the third night it was announced new people were arriving, one was a heroin addict! My reaction was of amazement and i made a tongue in cheek comment about hiding personal belongings...i thought as an alcoholic i was nothing like addicts...it was quite a learning curve cos the new guy and me got on like a house on fire and sat up till early hours talking every night...everything was the same, the feelings, the emotions, the way our drug of choice affected us etc...the only difference was the people, places and things...hell of an eye opener!
Then when i got to AA and got sober i met this great guy who went to NA and AA, and smoking coke was his thing...we spent a lot of time together discussing the steps, which one we were working with sponsor and other stuff...once again we were the same...then when i finished the steps with my sponsor in the first few months of AA things started to become really clear about all this...
I was really lucky with my experiences...
If i heard what you were told i would understand it as that a fresh alcoholic into AA needs identification with another alcoholic...and this would include the similarities in the people, places and things...this does not mean that addcits are exclusive to NA and vive versa for AA but that when sharing in AA stick to the drinking and when in NA stick to sharing about the using because although there will be a lot of cross addicts now there will still be pure alcoholics and addicts who won't connect with the other...
But like i said i do get where old timers are coming from with this and, although your reaction is very familiar to me, some of them are not being assholes just trying to protect AA/NA/GA and to ensure that we are of maximum service to the newcomer and don't lose too many that get to a meeting...hope that makes some sense....