[to Mr. Drayton, on patio] What happens to men when they grow old? Why do they forget everything? I believe those two young people need each other, like they need the air to breathe in. Anybody can see that by just looking at them. But you and my husband are … you might as well be blind men. You can only see that they have a problem. But do you really know what's happened to them? How they feel about each other? I believe ... that men grow old. And when the … when sexual things no longer matter to them, they forget it all. Forget what true passion is. If you ever felt what my son feels for your daughter, you've forgotten everything about it. My husband too. You knew once ... but that was a long time ago. Now the two of you don't know. And the strange thing ... for your wife and me ... is that you don't even remember. If you did, how could you do what you are doing?
[to Mr. Drayton, on patio] What happens to men when they grow old? Why do they forget everything? I believe those two young people need each other, like they need the air to breathe in. Anybody can see that by just looking at them. But you and my husband are … you might as well be blind men. You can only see that they have a problem. But do you really know what's happened to them? How they feel about each other? I believe ... that men grow old. And when the … when sexual things no longer matter to them, they forget it all. Forget what true passion is. If you ever felt what my son feels for your daughter, you've forgotten everything about it. My husband too. You knew once ... but that was a long time ago. Now the two of you don't know. And the strange thing ... for your wife and me ... is that you don't even remember. If you did, how could you do what you are doing?
http://www.moviequotedb.com/movies/guess-whos-coming-to-dinner/quote_67396.html