I have always heard that "you can never be offside on a throw-in".

Situation: Offensive throw-in. Forward is behind the defense and throw-in goes over defender's heads to forward. Forward takes the ball and starts dribbling towards goal. Linesman raises flag to call offside, stopping a sure one-on-one scoring chance.

Referee's explanation after the game: According to the linesman, the throw-in deflected off the head of one of the defenders, thus making the forward (who was behind the defenders) offside.

Looking for some referee input here. Was the correct call made? Whether or not the ball actually touched a defender can be argued. But assuming it did touch a defender before deflecting to the forward, does the touch by a defender automatically render the forward offside?

The ball needs to be touched by one of the attacking players not the defending. Refs sometimes make mistakes like not knowing who has the trow in thus making a bad call.

A/R and referee were both absolutely wrong. There is no offside receiving the ball directly or off of a defender from a throw-in. Offside position is recognized when teammate plays the ball, on the field of play, and is then penalized for gaining an advantage, interfering with play or interfering with an opponent.

Another commonly misinterpreted case:
While the ball is in play and played by an attacker, a deflection or a failed attempt to play the ball by a defender does NOT excuse an attacker in an offside position when his teammate played the ball.

If, for the stated scenario, the ball had been thrown in to attacking teammate, and he plays the ball off a defender to a teammate in an offside position, then offside is penalized.