I recently noticed that both Leta and Chuck stare at our naked bodies as if we are alien, particularly Jon. And if you think about it, the penis isn't a very friendly-looking organ. I'm not talking about one penis in particular, as I've seen more wee-waws than it would befit a proper Southern lady to admit, just the penis in general. It looks less like something that contributes to the genesis of life and more like a diseased tumor you might remove when performing an autopsy. So when Chuck seems a little frightened, makes sense.