I grew up with Lebanese Christians -- ACTUAL Lebanese Christians rather than those who just like to impersonate them -- and that's why I knew of the language and how it is distinct from Arabic.
Thus the three links I posted ........
Gardener, let me try to explain this to you as calmly as possible.
In Lebanon the official language is Arabic. All of the "Arabised" people speak Arabic but they have different Arabic dialects, more or less mixed with their original language, the languages of their invaders and colonisers.
All of the Arab and Arabised countries have in common the classical Arabic which is the common, official and administrative language. The newspapers are in classical Arabic, the radio, tv news as well as the language of discourses and official announcements.
There are dialects that are more or less simmilar. A Lebanese, a Syrian, a Jordanian and a Palestinian can understand each other perfectly well. We need some ear training to understand an Iraqi or a Kuweiti, as to the Egyptians we can all understand Egyptians because of the popularity of Egyptian cinéma.
It is extremeky difficult for a Lebanese lets say to understand a North African such as an Algerian for example, because as our Arabic is mixed with our original language and some Turkish words, their Arabic is mixed with Berber and French.
In short, you can get a Saudi a Lebanese an Algerian and a Morrocan in the same room and they will have trouble understanding each other but they can all read the same newspaper and watch the news on television.
When you say that my parents should have tought me Lebanese, it makes me giggle, because I speak exactly the same language that your Christian friend does. It's our common language, wether you choose to call it Arabic or Lebanese. I see it as 80% Arabic mixed with a few other languages . We learn classical Arabic at school. Both your Christian friends and I had school books in classical Arabic, read the papers in that same classical Arabic.
When you say my parents came from Armenia, they didn't, the Armenians of the Middle East came from Ottoman Turkey fleeing the genocide of 1915.
Hope this helps.