Is an organization like the Department of Homeland Security more of a protection for the American people or a potential threat to their liberties? Why?

While I fully understand the reasons for it after 9/11, I feel that it is used against people who are merely protesting against such things as the degradation of the environment (Ie oil pipelines on native land and water), to support native land claims, to oppose police violence against black people, to oppose unjust wars such as the war on Afghanistan and Iraq and Syria etc. In Canada, Bill C-51 is a so-called 'anti terrorist' bill but in effect it allows people to be detained and tried in secret and vastly increases police and secret service powers over the majority of people who simply exercise their democratic rights to freedom of speech which is supposed to be enshrined in the Canadian Charter of Rights and Freedoms. Even people protesting against 'infrastructure' ie pipelines, power dams can become criminals by this law.