"You proceeded without giving thought to whether or not the complainant was consenting or not.
"You pounced on this young man in a very compromising and vulnerable situation."
He said the victim, now aged 23, was at "no stage consenting" to the act and "just froze".
"He was out of his depth and didn't know what was going on."
He said the incident showed a monumental lack of judgement and thought on the part of the defendant.
The effects on the teenager had been significant and the victim was "mortified" at having to relive the incident through the trial.
"He still doesn't like having his photo taken or being in videos.
"He is yet to tell all of his family what has happened and may never be able to do so."
The judge took into account character references for the defendant and noted his prominent role in the community during the sentencing.
The man's fall from grace would be even greater when his name was released at the end of November.
Judge Neave said the man still showed a lack of understanding or remorse and "he had only himself to blame" for his sentence.
He said if he had pleaded guilty at an earlier date he would have had some credit during sentencing.
His lawyer, Roger Philip, said the offending was "opportunistic" and that he had contributed widely to the community in the many vocations he had.
"Beyond this offending he was a contributing member to society, perhaps more than most."