Rough ball play?

I met a guy on tinder and while we were getting busy, he reveals to me that he likes his balls played with a bit rough. I was intrigued because that seems so counter intuitive. I ended up slapping, squeezing, and flicking his balls a bit while we were having sex. He honestly really seemed to enjoy it even though he winced from the pain. I was just wondering if anyone else had an experience like this? Is it safe to play rough with the balls? Why do guys like this? Do any girls like it? I personally thought it was kind of fun but I was worried about his future babies :/
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