You should hear me trying to explain the phrase, "sucks shit" to some sort-of English speaking Cambodians. It goes like this:

"To suck is an insult because it all started I guess with sucking dick."
"What's dick"
"I mean penis, it all starting with women sucking penis. So if I say Cambodian food sucks, I'm actually saying that the food sucks penis"
"Why would food suck penis?"
"It wouldn't that's why it's a bad insult. The food can't suck penis, but if it did, wouldn't that be really bad?"
"Yes, it would" They reply.
Then I say: "Now sucking shit, umm remember I taught you that word, bullshit"
"Yes, we do."
"And how I pointed to that stuff of the road near the cows and said, that's bullshit."
"Yes, we do."
"Well, imagine taking a big straw and sticking it in the bullshit and sucking, like you suck Coca Cola with a straw."
"Teacher, this is really gross."
"Yes, I know. Sucking shit is gross. If I say Cambodian food sucks shit, this is a really bad thing to say about your food."