What specific illegal conduct did Ellsberg report? My understanding is that he leaked classified documents about the Vietnam War because he felt the public was being misled and had a right to know. That doesn't seem so different from the justification Snowden has given (assuming he's telling the truth on that).

How was Ellsberg "shielded"? He was put on trial, and Nixon famously sent the plumbers to dig up dirt on him.

If what you divulge is not illegal you have no protection.

What law are you referring to here?