IMO, nobody is talking about the play call...if it succeeded.
Many things went right for the Hawks on the play:
Lockette was open and Butler was the ONLY player in position to stop a score BUT he was 5 yards away from Lockette who was 2 yards out at the time of Wilson's release.
It was literally a 5 yard pass (maybe 10 with the angle) which is generally considered a low risk.
What made it fail were the mechanics AND Butler's knowing the play (Butler admitted to knowing the play right after the SB)
Typically, the ball on this pass is directed at the WR's midsection (keeping it low to avoid a tipped ball)
Wilson has a "low" release because of his height and cannot throw to the midsection or risk getting batted at the line which might end up with the same result.
His throw is a tad late and higher in trajectory which enables the CB to break a step before the throw is released.
Had Ben or Brady thrown the ball you can bet it is coming in hard and low allowing the intended target the only shot at the catch.
It doesn't much matter now but this could have been a successful play if Wilson delivers the ball a split second sooner, lower or at the WR instead of in front of him.
Butler knew what was coming...he said it himself. How he knew is conjecture and speculation. Great preparation or someone told him if they line up in a "stack", this guy does this and the other does that 9 times out of 10 or whatever. Having a employee on the staff to comb through a season or mores worth of formations and giving the coaching staff a ratio of likely plays IS a HUGE advantage.
I won't say it's illegal because according to the rulebook, it is not defined.
It IS however going to be considered UNETHICAL unless/until ALL teams play with the same advantage.
The NFL is powerless to do or say ANYTHING about it without potentially opening up a colossal series of bettor's lawsuits against it. That is why the evidence was destroyed. Common sense.