Your dad sounds like a fucking prick man. I know if one of my friends dad called my house telling my parents i smoke pot i would cuss them out like no fucking tomorrow. I would just looz it. And if he phoned my school telling people that shit, i would absolutly snap and cut him up to everyone i seen. I dont meen any offense from this but if hedid that to me everyone in town wouldnt even talk to your dad cause they would think he had some serious problems because i told them that. Like I dont know your friends parents or your friends for tha matter. But i dont take shit like that lying down. But my advice to blackmail him. Either that or just tell him to mind his own damn business and not to be a prick