Sorry, but you can protest otherwise all you want, but because of the way Laura set up the joke, it is a reasonable conclusion that she meant the joke to be interpreted that way. She set up the fact that Bush was such a city slicker by saying he tried to milk a horse. When she added it was a male horse, the joke got sent in a completely different direction. You may believe that she meant otherwise, but the dual inferrence was clearly there.
"but the dual inferrence was clearly there."
Like I said, you don't get it.