This is why you don’t have friends

I sat next to a dad and son on the subway today. The son was recounting something that happened at school. I think he got made fun of for having a "dad bod." He was probably 9 years old. The dad responded, "this is why you don’t have friends."

I was shook. Do I say something? Is it my place? Okay what if I say something right when I have to get off, so they can’t say anything back to me? I realized I didn’t have the courage so I just sat there and eavesdropped.

"You said you don’t want to be my father anymore."
"I didn’t say that. Stop making things up."

Silence.
Then a few moments later, the dad puts his hand on his son’s head and pulls him in close. They got off on the stop before me and hold hands.

Maybe things were okay after all. But after all my practice talking to strangers, what have I got to show?