It seems to me that Lake went to Wilmington intending to report on what was new with Pop Herring. Guy you profiled lands in jail, seems like he should be bailed out but hasn't been, you want to investigate. It's natural that your investigation will lead to you writing about it. And then, when Lake gets to Wilmington and learns that all Pop needs is someone to give $100 to get him out of jail, he does it.
But that's the difference I see—Lake didn't do this so he could write about it. Lake set out to write something new from the moment he got back in the car and drove back up to Wilmington to check on Pop Herring. What happened next, he didn't plan. Like a good journalist, he reported on it as honestly as he knew how.
The open letter is certainly a big risk. But then, because Lake seems like an earnest guy, what he ended up writing turned out to be what he felt most strongly. And isn't that what we're so often told makes for the most effective writing? To write with passion?
Others' passion may have led them to frame what they'd written in a different way. Lake was moved to write like this.
This is just my take, my interpretation of events based off the letter and then the interview Lake gave, so feel free to disagree. You won't hurt my feelings.