Ultimately, Boris brushes him aside.
The fact of the matter is this: being upward thirty years Tucker's age, there's a limit that needs to be set in place. Reputations exist for a reason, and continuing this would be damaging to both of theirs. Even if everyone uses a bank or buys a blender—scandal does neither of them good.
Not to mention the idea that Tucker is closer in age to his son than him is irksome in and of itself.
Boris prides himself in good decisions. He's built an empire on good decisions. He's moral and competent and knows what he's doing. Just as he thought, Tucker protests—using the word "protest" very lightly.
He should be flattered by this, he thinks. Tucker arguing for the sake of their "relationship" should be somehow moving and push him toward staying together. Tucker will cry and he'll see the error of his ways and they'll settle down in a fashionable district of New York, ignoring that they're both deathly ill and Boris has a son and—for lack of a better description—wife.
All in all, he is no monster. When Dieter escorts Tucker out of his home, Boris looks away.