How does Mitch respond to Blanches secret about her past?

Mitch responds to Blanche's secret about her past with shock and disappointment. Initially, he is sympathetic and seems to want to understand her struggles, but when he learns the extent of her history, particularly regarding her relationships and the loss of her young husband, he feels betrayed and misled. This revelation ultimately leads to a confrontation where Mitch becomes angry and rejects Blanche, highlighting the fragility of their relationship. His response underscores the themes of truth, vulnerability, and the consequences of past actions in "A Streetcar Named Desire."