Its like saying they saw a Catholic, or a Baptist....
If you saw Middle Eastern foreigners acting suspiciously, your wouldn't say they were "Catholic or Baptist appearing". Christian Arabs don't act much like Muslim Arabs.
The Arabs of the Levant are much more varied in appearance than the others. One Zionist novelist, he wrote in one of his books about how the character gave up on judging by looks, after seeing too many blonde Palestinians and swarthy Jews from Germany. The Palestinians, in particular, go all the way from looking quite African, to being peachy-faced English types.