Are that Many People Really that Clueless?
The age difference is a major plot point. In fact, it is the crux of the movie along with his playboy lifestyle. He is an aging skirt chaser.
I don't find the movie far-fetched. If it disgusts you for people to fall in love, don't watch. Hell, if you're all that puritanical, maybe you shouldn't be watching movies at all. Don't drink alcohol, play cards, dance, or sing. Singing is acceptable if the songs are in praise of the Lord.
The best diplomat I know is a fully charged phaser bank.