Here's something mankind has known about intercourse since the very, very first sexual act was performed: If in describing the act, the words "bite" and "scrotum" appear in the same sentence, something went catastrophically wrong. So wrong that your behavior should have earned you an unceremonious exit from the gene pool.
To put this in context, when kangaroos fight each other, they use the claws on their hind legs to tear at their opponent's scrotum. Even when trying to kill each other by way of scrotal trauma, wild animals refuse to go so far as biting.
And by the way, when dealing with teeth and that area of the body, the modifier "softly" doesn't do anything to make this better. That's like saying to "gently" jam a lit cigarette into his eye.