These people are supposed to protect us

We've already heard many stories about how the CIA, military, cops, justice/penal systems, and Secret Service have really messed up and violated the public trust. Apparently most other agencies are not immune either:

The FBI admits to overstating the conclusiveness of forensic biological evidence (hair) - hundreds of cases potentially tainted since 1972, incl. dozens of death penalty cases: http://www.washingtonpost.com/local/crime/after-fbi-admits-overstating-forensic-hair-matches-focus-turns-to-cases/2015/04/20/a846aca8-e766-11e4-9a6a-c1ab95a0600b_story.html

DEA agents attended wild sex and coke parties for years in Colombia, paid for by local cartels: http://www.usatoday.com/story/news/nation/2015/03/26/dea-brothel-prostitutes/70482964/

What is the point of funding these people and giving them broad powers, when this is how they serve us? I know plenty of security personnel are diligent, good people, but then they have a duty to call out or root out the bad ones among them. Their mission is to protect America against external AND internal threats, right?

At least I haven't heard any bad stuff about the Coast Guard. Well, they do interact with smugglers and cartels, so the opportunity for corruption is also there.