Penetrating a close-knit Orthodox community might not be as easy as they think. Conservative Judaism somewhat easier, and Progressive Judaism the easiest to the point where they could dress as Muslims because the Progressive Jews like Muslims more than they like the Orthodox, and would gladly invite them in, weapons and all.
Probably not a good idea to try and infiltrate a group of Zionist Israeli Jews, as the Muslim might quickly find himself dangling from a light pole.
You’re correct. I think you make a mistake assuming this tactic is meant to be used in Jewish communities, though the instruction, does this rise to a fatwa, suggests that. But it makes no mention of Israel. This tactic has worked in Israel, but would be more effective in the US and Europe. Muslim women could do it too. The key is a rationale for wearing clothing adequate to conceal weapons. If the morons knew more about the world outside the Mideast they’d know for half the year they’d be less obvious in half the US dressing for winter.