For Ellsberg I'll just paste my comment from below:
My opinion is that Daniel Ellsberg supports Manning for the simple reason that it aids his own activism, even if the facts are not 1:1 the same as his case was.
And that's kind of an important point: Ellsberg helped author the Pentagon Papers and knew full well the import of what he leaked (to an American paper, btw, not Soviet, N. Vietnamese, or neutral party). Despite having a Top Secret clearance Ellsberg didn't leak other classified information that he may have had access to, as it didn't pertain to the lies that the government was feeding the public at the time.