The Executive Branch enforces, the Judicial judges. The Constitution says it quite explicitly in Articles 2 and 3.
You give far too much credit to politicians. They don't think of this as security vs. freedom, they think of it as power. Power for them, power for their party, power for their people. It's a simple explanation, but it fits. Heck, research has even shown that politicians will decide based on what keeps them in office, not what they "should" do [1]. Jefferson said it best:
"All men having power ought to be mistrusted. Perhaps it is a universal truth that the loss of liberty at home is to be charged to the provisions against danger, real or pretended, from abroad."
[1] Congress: The Electoral Connection by David R. Mayhew
You give far too much credit to politicians. They don't think of this as security vs. freedom, they think of it as power. Power for them, power for their party, power for their people. It's a simple explanation, but it fits. Heck, research has even shown that politicians will decide based on what keeps them in office, not what they "should" do [1]. Jefferson said it best: "All men having power ought to be mistrusted. Perhaps it is a universal truth that the loss of liberty at home is to be charged to the provisions against danger, real or pretended, from abroad."
[1] Congress: The Electoral Connection by David R. Mayhew