"If it doesn't feel right, it probably isn't"

(Anti-terrorism sign seen on New Jersey Transit)

To protect ourselves against the likes of the Boston Marathon bombers, the D.C. snipers, and potentially much worse, we have to help each other: everyone has to be involved. It's a primary rule of a community under threat.

But wait a minute: Does that mean we should report anyone who looks funny, or who makes us uncomfortable? Isn't that a recipe for fascism? To avoid terrible risk, do we have to revert to totalitarianism or communal conformism?

There's a great danger now of a retreat into ever-narrower communities with strong loyalty tests. Anything we don't understand, anything that doesn't "feel right", is a threat. This goes against the grain of American history, of the embrace of diversity, of widening nets of communication and exchange over the past century or more. But is there a choice now?