It usually DOES NOT mean those sort of sexial activity or something.

愛の鞭 (Ai no muchi) is an idiom often used by stupid teachers when they scold or punish their students. (Possibly this is my prejudice. I personally hate this idiom because it soounds crony and somewhat dishonest.)

They would say something like "I scold/punish you not because I hate you but because I want to help you. I hope you'll be a good child. In short, I whip you because I love you." Thus, it is a "whip of love."