Banning the_donald would stir up a pointless gigantic "censorship" shit-storm. A similar sub would emerge within a few days. It's not worth the drama.
The world censorship also carries implications about the motives of the supposed "censor" by alluding to the notion that their actions are motivated by a desire to silence a message that they fear or disagree with when other explanations could be more likley. For example, maybe you don't care if the message is heard, but you just don't want to hear it in your house... if you then kick me out your house, that doesn't mean I'm being censored, it means that what happens on your property is your prerogative. Maybe you didn't even hear the message and just don't like my tone or maybe you did hear the message and find it to be worthless, it's not censorship if I ban you for stating that aliens orchestrated 9/11.
Banning anyone from reddit is not censorship because they were never entitled to the use of reddit's privately owned property and reddit's actions do not impede their free expression through the use of their own resources.
I think we’re well beyond the point it’s time to have a national conversation about how these private companies exist as the public commons nowadays. They make these entirely capricious and disgustingly transparent swings between “Place for open discussion and free speech” (actually the founders exact words in many an interview in Reddit’s case) when the owners want attention and hype and warm fuzzies from the user base, “private company” when it suits their needs or they’re challenged on their principles.
Reddit is beholden to their shareholders, not their users.