Re: 509 - 5. The Diner.
I think Justin knows that his mother's relationship with Tucker is similar to his own relationship with Brian. Maybe Justin doesn't want his mom to end up like him and Brian did. Maybe he thinks she wont get what she wants with Tucker, which Justin might think is what he wants with Brian. A real, mature relationship. He thinks if he couldn't make that kind of relationship work, neither can his mother. And he just wants to protect her from the misery he had to go through with trying to make his own relationship work. I hope I made myself clear ^-^