How does Flan react to Paul saying Flan is his father?

This is the scene:

PAUL. You’re just like my father.

OUISA. Which father?

PAUL. Sidney! (Pause.)

OUISA. Paul. He’s not your father. And Flanders is not your father. (Flan comes in, fully dressed).

FLAN. Oh fuck. We have drinks with the Japanese at six fifteen Get off that fucking phone. Is it that kid? Get him out of our life! Get off that phone or I’ll rip it out of the fucking wall! (53).

OUISA. He wanted to be us. EVerything we are in the world, this paltry thing our life he wanted it. He stabbed himself to get in here. He envied us. We’re not enough to be envied.

FLAN. Like the papers said, we have hearts.

OUISA. Having a heart is not the point. We were hardly taken in. we believed him for a few hours. He did more for usin a few hours than our children ever did. He wanted to be your child. Don’t let that go. He sat out in the park and said that man is my father. (Guare 54-55).