In your estimation, are you placing the very active and loud anti-corporate voices in this country outside of American politics, or merely denying that they are genuine?
Thankfully in the US the people have a lot of power, and Sanders is active in politics no matter how much the "powers that be" attempt to dismiss him.
Warren is also anti-corporate, though I'll admit I don't know the extent, and I think she is easier to see as a mainstream democrat than Sanders is.
My point being Sanders may not be accepted by the mainstream, but this is an unprecedented (since the 50s) level of acceptance of a class perspective. I'm not sure why you would explicitly ignore this change of events.
Bernie has/is changing that, but even then I would argue the main power structures haven't changed.
Bernie isn't / hasn't changed anything and won't. Sanders comes at the problem from a position that is considered Socialist (even though he's only a Socialist in name for the headlines), which will keep him forever in a cordoned off box. The last force in US politics with any influence in that regard, was Ralph Nader. He accomplished greater than ten times what Sanders has or will (and given his age at this point, the clock is ticking) when it comes to anti-corporate power checking. The Democrats lit Nader on fire and buried him politically for opposing their establishment one too many times.
Certainly, the people in control of the Democrats (such as superdelegates) did not choose an anti-corporate message in the last presidential election.
Could you clarify which voices you mean?
It's a benign argument. I wonder why his opponents hyperventilate and exaggerate his positions...