While doing homework for "Introduction to Mathematical Thinking" course on Coursera I came across the phrase "Everybody loves a lover". At first I thought that the meaning of it is straight-forward, but then the task description said it was an idiomatic expression. The exact problem description was:
Which one of the following means "Everybody loves a lover", where L(x,y) means (person) x loves (person) y and a lover is defined to be someone in a mutual loving relationship? (If English is not your native language, you might want to discuss this sentence with a native English speaker before you answer. It's an idiomatic expression.)
I couldn't find the meaning of it on the Internet, so I'm asking here: what is the exact meaning of this expression?