I think it's realistic to have hope. One can be a perverse idealist and say the easiest thing: 'I despair. The world's no good.' That's a perverse idealist. It's practical to hope, because the hope is for us to survive as a human species. That's very realistic.

This quote suggests that it is better to have hope than to be a “perverse idealist” who believes the world is not good. The speaker argues that having hope is better because it is realistic to hope that the human species will survive. In other words, it is important to stay positive and strive to make the world a better place so that humanity can survive and thrive.