Justify it however you like, Freddie Freeman was kept to be the face of the franchise. Had he not been, "regular fans" wouldn't have gone to the park for several years. The Mariners are looking for the same type of overpay to move Haniger that it would have taken to get the Braves to move Freeman several years ago.
I'm not arguing whether that's the best way to run a franchise these days but given the fact that the Braves are simply an extension of the corporate entity that is Liberty Media, the bottom line did make a bit of a difference. The Mariners may be in a position that their owner's willing to have 10,000 people show up at the park every night like the Marlins do, but it certainly doesn't appear they are. If they are able to turn this around within a couple years, Haniger could very well still be a valuable contributor.
Not trading Haniger could prove to be a mistake, sure. From the standpoint of NOT trading him unless you're blown-away, I'll offer this...
If the Braves had traded Freeman for a handful of prospects 3 years ago, they don't make the playoffs in 2018 - and aren't CLOSE to the position they're in right now. The ifs and buts are endless, but the chances you actually get someone in a return for Freeman or Haniger that actually measures up to them 3 years from when you trade them is on the south end of slim and none. Anybody that argues differently spends a little too much time with their calculator. Keeping the face of your franchise guarantees you nothing other than that you're not chasing players for $300+ million that have never won anything - including enough respect to be considered the leader of your team. Guys like Freeman and Haniger (and Chipper and scores of other ones before him who weren't just about the bottom line) will never measure up to the Harpers and Machados on paper. They also won't have near the challenge of being a leader that guys who tell you point-blank that they're not "Johnny Hustle" or are busy trying to build their brand with hair commercials will have when it comes time to asking teammates to follow them.