Why are Bruin fans so in love with Anderson? And why is it always Hainen going the other way?

not entirely sure but Anderson is a fantastic defensive forward with a physical game. Boston type of player.

Don Sweeney out here playing Franchise mode with trade difficulty set to Easy

If he’s that type of player wouldn’t Columbus want to keep him? Honestly I don’t think he’d help Boston that much and the bruins would be better off keeping Hainen.

he seems to be the type of player any team would want but I think there was some rumour of Columbus considering moving him related to a previous contract dispute which i think was last year.
I don't think Columbus moves him unless they enter a full rebuild which they really don't need to do since they have two star defencemen, a young team and a lot of cap space

The contract issue was 2 off seasons ago, and this year there won’t be an issue getting him signed due to the arbitration hearing. The only reason we really should sell him is if we can get a 2nd line center back(Anderson would be part of the trade not all of it) or if we truly think we’ve seen the best he has to offer.