You already do: how often do you penalise a scrum half for hands in the ruck?You may not like it, but that's what the law says. We can't just referee the laws we like and ignore the others can we?
[LAWS]A player must not tackle (or try to tackle) an opponent above the line of the shoulders even
if the tackle starts below the line of the shoulders. A tackle around the opponent’s neck or
head is dangerous play.
Sanction: Penalty kick[/LAWS]
You are arguing that making high contact can NEVER be accidental. Unusual, yes; impossible, no.
The advice is unrealistic. Going for the ball is a standard technique in appropriate circumstances.There is no law that says it doesn't apply if the tackler is 7 foot tall and the ball carrier is 5 foot short....or if the ball carrier makes himself shorter by bending over. If you tackle low and legally it will never be a problem.