The world is full of strange customs. I was thinking that this is somehow a Vietnamese custom that had somehow escaped our attention. I was thinking that perhaps it was something that had been observed. I am told that in Biblical times there was a practice of holding the testicles of a man as an oath. They apparently did not see this as sexual behavior. It's possible (by some stretch ofr the imagination) that the described behavior isn't viewed as sexual in the context. We kiss babys' bottoms and it isn't sexual. Of course, it's possible his intent was simply to shock the reader, a form of exaggeration for a point. I don't know. It's just so out-there. Pray tell good sir, in what part of the bible will I find two men holding each others balls as they confirm an oath?
Perhaps, you could show me the passage where a woman, by use of her vagina muscles, parted a banana into fourths.