Why is Moose both proud of his mother and angry at the way the meeting with Mr. Purdy turned out in Al Capone Does My Shirts?
Moose is proud of his mother's courage and persistence in standing up to Mr. Purdy. Although she accepts that Natalie will not be allowed to stay at the Esther P. Marinoff School at the present time, she will not leave until she has extracted from Mr. Purdy some suggestion or element of hope that she can pursue in her quest to enable her daughter to lead a meaningful life. Mr. Purdy clearly just wants Mrs. Flanagan to take Natalie and go, but Mrs. Flanagan is "unstoppable," badgering the man until he finally offers to put her in touch "with someone who might be able to help Natalie."
On the other hand, Moose is also angry at the way the meeting between his mother and Mr. Purdy turns out, because he knows that no matter what this contact that Mr. Purdy has given her involves, she will follow through on it, whether it makes sense or not. Moose remembers that his mother once sent away for voodoo dolls and followed the instructions of a West Indies witch doctor in an attempt to cure Natalie's condition, and even here at Esther P. Marinoff, she had left Natalie behind, screaming in terror, in blind hope that her daughter might be healed there. Mrs. Flanagan is so desperate to find relief for Natalie that she will do anything; she is incapable of entertaining the possibility that things with Natalie might never be normal, and that she might never find "a happy ending."