Fascists and white nationalists defend it by claiming it's just clownish fun. (which, unamusingly, is EXACTLY the same explanation given by the supporters of fascism in Italy, and Russia, and Germany). Trolls really are having fun, they just don't give a fuck.
It's propaganda. It's gross. All of the donald's loser readers and writers have the right to share their bad ideas; but they have no particular right to say it on Reddit.
Jon Stewart doesn't get to make Fox News carry his show unedited (or at all); and Reddit also has no particular responsibility to provide a platform for your fascist cronies.
I explicitly support your right to have bad ideas and to spread propaganda and lies. And you can do some on Voat and Gab and a host of other places that welcome your bullshit.