Some hold that restricting human rights is a necessary if unfortunate cost of preventing terrorism. Others conclude that such abuses aggravate political grievances that contribute to terror. We demonstrate that theory and data support the latter position. (source)
They focus on what they call physical integrity rights, or rights which protect people from physical harm. The more a state respects these rights, the less terror attacks it suffers. It will also be less engaged in some way or other in transnational attacks.
These findings are opposed to two similar and widespread beliefs: unstable states can only guarantee security is they are authoritarian (see here), and even well-developed democracies have to limit some human rights in order to fight a terrorist threat. In the former case, the threat comes usually from within; in the latter case from abroad.
States that seek to preserve human rights and political freedoms are limited in their ability to monitor and detain terrorism suspects, are prohibited from making broad police sweeps to catch terrorist perpetrators and their sympathizers, limit coercive interrogation of suspects, and must afford suspected terrorists access to a lawyer and a public trial. Freedom of assembly and of the press allows terrorists and their supporters to publicize their grievances. … The implication is that states that protect human rights are more vulnerable to terrorist attacks. (source)
In fact, the opposite is true. Protecting human rights, and especially security or integrity rights, reduces terrorism, and violating them promotes terrorism. Terrorism is a complex phenomenon, but I think it true to say that grievances and injustices (and many of those are caused by rights violations) are important motives. Democracies and states that respect human rights supposedly give too much freedom to terrorists, allow them to organize, recruit, mobilize and plan, and make it very hard to efficiently combat terrorists (rule of law, free speech, humane treatment and torture prohibitions etc. are all said to hamper counter-terrorism). But authoritarian regimes create injustices on which terrorists feed. They also make it hard to express and redress grievances in non-violent ways, and use ruthless methods that only make their opponents more radical, fanatic and popular.