The most obvious approach would be to wait until someone's given you at least the tiniest hint that they could possibly be planning on attacking you before treating them as a potential enemy.

What kind of legitimate threat would the US government even be watching out for with the German Chancellor? Are they so paranoid that they think the Fourth Reich is just over the horizon, or did Merkel's statement that "Islam is part of us" tip them off that she might be running a terrorist sleeper cell?