i've never had a problem, from either the one being played with or the one playing with them. they're just balls. you can tongue them, suck them, fondle them, play gently with them just like you would any other body part. they're sensitive. some guys hate having their balls touched/played with, some love it, just like some women and men hate and/or love having their nipples played with. it's really up to whoever's playing the guy what they'd like.

suck them. fondle them. hold them lightly. tease just behind the perineum. hold them in your char's mouth and hum. i feel like people that can't write about them are also people that haven't actually played with them in real life, so they have no frame of reference. ask about it if you'd really love to involve them. there are plenty of male rpers here. someone asked about the distance of ejaculation. ask about balls.