I'm no expert in these "advanced stats", but shouldn't the final scoring margin be subtracted as some kind of normalizer? Otherwise you're just showing that that player was on the court a lot in a game where their team got blown out.
EDIT: Or better yet, subtract final score margin x minutes played/48. If this statistic doesn't exist yet, I would like to name it "Playing Time Weighted Normalization of +/-". Or "PLATWENO+".
Couldn't you say that a player with a lot of defensive rebounds in a game "was just near the basket when the opposing team missed a lot of shots"? You could, of course. But so what? A stat is just a stat.