You shouldn't rain on an optimist's parade.
Antonio listens as his mother talks about how a politician, who is consistently corrupt and cold toward the people, will make the world a better place eventually.
Antonio wants to respond to his mother about this politician.
Antonio listens to his mother and responds that she always sees the good in people, but that she should also look at the politician with a critical eye.
Antonio lists all of the reasons why this politician is a terrible person and will never do anything to benefit anyone but himself.
His mother is happy that he sees her intention to see the best in everyone, but she understands his point that it is good to be a realist as well.
Antonio's mother feels that the politician is being attacked and tries to assure her son that he just misinterprets the political environment, and that he is actually doing good.