Ummm...no. I have to disagree on at least one point in your "statement, not a discussion
SHIELD works for the UN.
Marvel/Disney gets away with saying it flat out in the comics for reasons unclear to me, but in the movies they have to call the people that SHIELD's Director reports to the "World
Security Council". Otherwise, the UN's trademark/copyright-defence lawyers get all cranky. Therefore, not
a "shadowy cabal". Putting the Security Council members in shadow in Avengers
was a nod to how Fury Sr.'s bosses used to be depicted in the comics, but explaining that further involves a lot of continuity stuff that people don't like to make newcomers get into.
There was a similar fuss over UNIT in Doctor Who
a few years back, as Whovians will definitely recall. The UN didn't want their name to be part of the full spelling-out of that fictional organization's acronym anymore after that TV series was revived.
Also, one of the long-haul arcs of Agents of SHIELD
on TV appears to be the organization's process of learning how to live and work in the open, as spearheaded by the regular cast. I wonder if Coulson's roving field team has realized that this is what they're doing, but at least one other reviewer's made an interesting case over at tor.com.
Whether or not the organization as depicted across the TV/Movie is a "secret police" regime...well, some
of the characters are going to want it to be exactly that. That's part of the point of Winter Soldier
next spring: having that argument play out amongst the characters. A battle for the soul of SHIELD...one that's been playing out for decades in the comics themselves.