Nathaniel was planning on leaving this country after a while. That's why he was open about criticizing Leander. Also, he did not like that his mother is considering Leander as her son too.
He didn't know how Leander found out about his plans to leave but he knew the reason Leander is bringing it up now.
"I know a very good gynecological surgeon. I'll arrange everything. Trust me, Capo, I can keep a secret. Please, leave my family out of it," Nathaniel begged, tears streaming down his face.
He knew the risks of getting involved with the mafia family. But he did everything for his family. He cannot lose them. All the mafia family wants are mindless robots who follow orders perfectly. It was his fault to overstep thinking that he can actually leave.
Leander threw Nathaniel over the butcher's block and stormed out of the room not before giving a meaningful glance at Steve.