Be wary all you want for whatever reason.  But allow others to be wary as well for good reasons.  The Boston bombers and the 911 hajis had assimilated into middle class America and were "good friends" with their American neighbors.

How many Americans have beheaded other humans for religious reasons?  How many Americans have thrown homosexuals off rooftops?  How many Americans have put their wives in a hole in the ground and stoned them to death for "infidelity"?  How many Americans demand that other humans convert to their religion or die?