It doesn't matter one whit whether Lamo offered protection or not, except insofar as what you think of Lamo.
The shield law doesn't require journalists to keep info private -- it simply allows a reporter to quash a subpoena from law enforcement coming knocking for the info.
If indeed Manning had taken Lamo up on the offer, at best, Manning has a civil case against Lamo.
And as for Lamo being a minister, that's a joke. Knowing Lamo he's got a minister certificate he bought for $25 just to say he has it. Furthermore, Manning didn't take him up on the offer and the chats certainly don't look like a minister and a worshipper talking.
While it's clear Lamo is double-crossing Manning and trying to suck info out of him, this bit of the chat logs don't mean anything substantively.
But folks like Greenwald need a nemesis, so any point to beat on Wired.com for reporting the story will work.
Full disclosure: I work for Wired.com and Kevin Poulsen used to be my editor, and still occasionally is. I never saw the logs till they were pubbed and had no hand in the decision.