Well, for the same reason that laughing at a rape joke, a racist joke, a child molestation joke, a murder joke, or someone walking face first into glass indicate that I live in a society that is friendly and accepting of racism, rape, child molestation, murder and all the rest so too it must therefore follow that the United States is friendly to Nazis. Because, you know, I laugh at Nazi jokes.
Now, don't let the fact that we've gone to war and killed millions of Nazis, routinely imprison murderers, rapists, child molesters and all the rest counsel otherwise. Laughing at a joke quite obviously indicates one lives in a society that is friendly to whatever is the underlying story of a particular joke.
Tosh made a joke about rape (or a comment depending on what one reads) or some such. And that, of course, translates to the whole of society being supportive of actual rape - not supportive of jokes. No sir (or ma'am). Laughter quite obviously to the culturally and socially plugged in people who just 'get it' supports not comedy, not humor, not laughter, not irony, but rape. It couldn't be anything but.
When will you fuckers learn that you can stop all the ills of the world by not laughing? Mel Brooks, shame on you.