I think you'll find that the club expects players to be a lot more like the Neville brothers than you could imagine. Like them or not, they were model professionals who did not (to my knowledge) disrespect or embarrass their clubs or their families.
Foden and Grealish acted like a pair of thick schoolkids - they were probably laughing behind Pep's back after he censured them. Foden needs to grow up and spend his free time being a decent father to his children rather than drinking and seeking out prostitutes.
As for Grealish... He got into his car when drunk, with the intention to drive. Not only is he a dickhead, he's a dickhead who could have killed someone. He's a wrong 'un and a bad influence as far as I'm concerned.