What sets off the very first argument of Act II?

When they discuss their marriage, Amanda asks Elyot if he had an affair with a woman she suspected him of seeing after the divorce. When he confirms it, she is initially taken aback, but admits that she did not expect he would remain any more celibate when they were divorced than she did. The thought of Amanda being with other men angers Elyot, who finds it improper. They do not, however, need to call out "Sollocks."