You're semantically quibbling with a clear joke and using those quibbles to avoid engaging with the point it's making.

> "Selling is legal, and fucking is legal; but selling fucking is not legal."

I don't get it. The literal interpretation is a clear joke, as you say. So what's the point that it is making?

To be clear, I think the law discussed is stupid. I also think the argument that if both parts are legal they should also be legal together is wrong. What am I avoiding?