Nah, I don’t find that particularly weird; after all, how many non-Arabs are there who are really fluent in Arabic?

I get the same with Russian all the time; given, my family is from that (very) general neck of the woods (though we are obviously far from being Slavs), so there is reason for the physical resemblance to a native speaker. However, one would have to go back several generations to find someone who lived in a region where Russian speakers were in even a substantial minority (western Ukraine, the part that was in Austro-Hungary, may have had some Russian speakers, but not tons – same for very early 20th century Latvia), and nobody else in the family speaks any Russian (except a cousin who studied it in high school).

The assumption is not quite so prevalent now that more Westerners travel to the CIS, but in Russia I am frequently mistaken for a native (or quasi-native) speaker, usually Armenian, and upon my return to the U.S. in 1990 native speakers frequently asked how old I was when I emigrated to the U.S. from, say, Azerbaijan. (Apparently the distinctive Caucasian accent persists 15+ years after the ex.) Heck, I got mistaken for a Georgian just last week. And the little old Armenian grandmothers in the farmers’ markets in Russia would usually give me a big hug and explain that we are all the same, because the Armenians are really one of the Lost Tribes, and Noah’s Ark is buried in the side of Mt. Ararat.

That's funny that people should assume one is necessarily Muslim for speaking Arabic. When I was growing up (in CA), quite a few of my friends were Christian Arabs and I was possibly one of a handful of people in States who was rather shocked to find that Xian minorities in Syria, Palestine, and Egypt are much smaller than I had always imagined them to be.....

Still, in the States, the population figures are such that an "Arab" immigrant is more likely to be a Xian than a Muslim, for now, at least (my info may be a little bit out of date by now).

To use Occams' razor here, the assumption is probably due to the fact that most Europeans and Americans have a hard time with Arabic because of the required sound set has phononemes that are hard to acquire when one is above the age of 14 or so, grammar acquisition would follow the same pattern.

That people who speak Arabic fluently will tend to have some familiar connection to the region would be the experience of many, and we humans tend to synthesize the 'best explaination' by turning an observation into an explaination without hypothesis testing and the like.

This is a variant of the old English adage "Blood will tell", that ones' breeding will show through in one way or another.

People believe weird shit all over the world. My noble wife Filipino popular culture believes that if a Filipino doesn't eat rice for 2 days running, he/she(literally, in Illocano, the third-person singular pronoun is gender-neutral) will suffer from stomach aches and other problems almost as bad as a junkie going through heroin withdrawl.

The Chinese tell their children to clean their plates because every grain of rice left is a pockmark on their future spouse.