... to a story NBC did a long time ago in which they edited the audio of Zimmerman's 911 call. The editors note is just to let the reader know that there may be a conflict of interest in things they write about Zimmerman.

http://www.washingtonpost.com/blogs/tv-column/post/george-zimmerman-sues-nbc-for-defamation/2012/12/06/ae15b972-3ffb-11e2-bca3-aadc9b7e29c5_blog.html

For whatever it's worth, I think NBC was guilty of incredibly bad journalism in editing the call. I don't know if that's defamation, but it was terrible reporting.

and wondered what would posses a journalist to tamper with that kind of evidence.

If you remember NBC/MSNBC went on a ratings grab (for the best of intentions, i am sure) and decided to present a "altered" version of the 911 call without attributing it's alteration.

The tape as it existed was just not in line with the story and ratings they wanted.

tape to make a point that was not made in the original.

does not make it any better or less dishonest. Nor does it make MSNBC a "news" channel any better and easily arguably on the same level as fox...perhaps a bit lower, since MSNBC only cares about ratings and they have no current programming covering news as anyone would recognize it, just talk show hosts 24x7 - minus prison channel time of course.

The editor's note might be there in the same way you'll sometimes see other possible disclosures a news organization has a connection to a particular story (ie: such-and-such company is owned by so-and-so company, which is also our parent company)

it's not about that article. His lawsuit filed last year concerns NBC editing the audio of his 911 calls in reports last year.