Pine tar didn't give up four runs to the Yankees last night. Pine tar didn't stop the Red Sox from hitting once Pineda had left the game. Could the pine tar have helped Pineda's grip, and thus his location? Probably. Is using a foreign substance against the rules? Yes. But let's not pretend Pineda is the only guy who does it.
Our very own Clay Buchholz withstood a media firestorm of his own last year when he dominated with some alleged help from Bullfrog sunscreen. Most managers are loathe to alert the umpires when an opposing pitcher is using some sort of topical assistance, because they know it's likely their guys are doing something similar - and as a former pitching coach, John Farrell has to know the hands of his staff are probably sticky, too.
Pineda's use of pine tar seemed to be particularly blatant - NESN analyst and former Red Sox pitcher Dennis Eckersley called it "outrageous." But everyone seems to agree that the substance on Pineda's throwing hand was gone after the fourth inning - and he didn't start falling apart until the seventh, when he was coming up on 100 pitches.
So maybe the pine tar (or whatever it was) helped Pineda when it was on his hand - but it wasn't the reason the Red Sox lost the game.