A friend of mine wants me to kick him in the balls because he likes it... wtf do I do?

it sounds funny but also weird as hell. He told me a while ago he has a kinky fetish and thats good and all but he’s my friend and I don’t know how I feel about it. On one hand you don’t get to hit guys there freely ever and on the other he’s my friend and I don’t want to hurt him? What does everyone else think? Has anyone ever been in an even remotely similar situation?
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