So does the bill of rights/constitution and many other things. Rights and humane treatment can benefit bad people who take advantage of it. The issues is that a lack of rules and accountability is more of a DETRIMENT to honest, good people (and benefit to corrupt, bad officials, etc) than it is beneficial to terrorists.
Or, as put by H. L. Mencken
"The trouble with fighting for human freedom is that one spends most of one's time defending scoundrels. For it is against scoundrels that oppressive laws are first aimed, and oppression must be stopped at the beginning if it is to be stopped at all"
This also applies to covert/illegal surveillance, etc