Being Muslim seems consistent with what we know about it:
A) They did a bad thing.
B) Their religious persuasion was not mentioned.
Thus, they are certainly not Jewish or Christian, else their religious persuasion would have been reported. But if they were Muslim, it is a risk to mention it, lest the writer be accused of prejudice.
Tthe fact that they called her a “Dirty Jew”, is consistant with them being Muslim. Definately not Christian Arabs, nor Jewish Arabs.