So I assumed this thread was about Superman being an 'outsider' because of his alien origins and his powers - not being an 'outsider' in a political sense.
That said, I realized something interesting about Superman and his politics (or lack thereof).
The Golden Age Superman, as I mentioned, probably didn't really feel like too much of an outsider...except perhaps in his role as a 'mild-mannered' reporter, which was pretty much an act back then. But he was a 'champion of the oppressed', a vigilante who fought against the oppressive powers of the status quo and stood up for the little guy.
In stark contrast, the Silver Age Superman felt like an outsider because of his knowledge of his alien identity, and his preoccupation with it, but was a defender of the status quo and very much an 'insider' in that sense.
Which makes me wonder...does Superman feel more free to take a stand against the status quo when he is secure in his identity as an immigrant human and feels at one with humanity? Does he gravitate towards the establishment and the powers-that-be of human society when he's less secure about his place among humans?
This reminds me of that scene in Quest for Peace where Superman goes before the UN panel and claims that he's always considered himself a visitor and an observer on earth, which is why he hasn't interfered in global issues - but now he's "no longer just a visitor" and considers himself as belonging to the earth, which is why he's taken a stand on nuclear disarmament.