It's not the word itself. The word could be "terrorist" or "bomb" or "Muslim" or anything, really. It's denying some wrongdoing without having first been accused of it. Humans learn very early on to be suspicious of people who offer denials prior to accusations, and we likewise learn in childhood not to offer such denials ourselves.

When no one has accused you of stealing a cookie from the cookie jar, saying out of the blue, "I didn't steal the cookie from the cookie jar" instantly makes you a suspect. This is Encyclopedia Brown level stuff.

(As an aside, your lack of intuitive understanding of this principle, combined with your righteous indignation and judgment of the world at large, makes me feel very much like you describe while writing this reply.)