There's a few dubious claims in Cameron's article. If everything he says comes true, then of course it's a good trade for the Tigers.
First of all, it's this whole love affair with WAR that I still don't think has any bearing on the game. Without going into massive statistics in this post, Kinsler's WAR in the last 5 seasons is 24.2 (bbr.com) with an OPS+ of 107, and Fielder's is 19.2 with an OPS+ of 147. Obviously defense is in there, but these numbers just don't add up for me.
So blindly saying they swapped one 3.0 WAR player for another, implying they are totally equal value players, is silly. (By the way, neither player has ever had a 3.0 WAR!)
If Fielder continues his mediocre offense from last year, clearly it's a good trade for the Tigers. If he has a bounceback year at 30 (no reason he couldn't!) then he's clearly a much, much better offensive player than Kinsler.
Also, Cameron claims that it will "keep Cabrera healthier". Well, maybe... who knows? I suppose moving to first might be better for him, but he still has to play the field every day. Just making that claim doesn't necessarily make it true.
All in all, it could be a good move for the Tigers, but it's not so cut-and-dry. This could also work out great for the Rangers. There are only so many premier hitters in the league, even at 1B. Until last season, Prince was certainly among them.