How to deal with stupid dad?

[GarthB]

At the youth level, ignore him unless he is addressing the players and becoming a distraction to their play. If he is, ask the appropriate coach or authority to address the issue.

At all levels higher, ignore him. Your job is to see that the game is called with equal regard to the rules for both sides. Your game is on the field, not the stands. If you're bothered to the point of losing your concentration by someone showing their ignorance, you have the wrong avocation.