The problem is not the roles, but how those roles are carried out and the complete lack of accountability. It's difficult for citizens to believe that government agencies are noble endeavors when we see ever-creeping anti-Constitutional scope, and rampant unpunished criminality among their members. It would be fantastic if this weren't the case, of course. Unfortunately the only check mechanic we the People seem to have is to consider them hostile entities best avoided until they're drastically reformed.