r/The_Donald is banned from being a default subreddit while /r/politics is not. That matters because users without accounts or who aren't logged in will see content from r/politics if an article is trending but not an equally trending(?) article from r/The_Donald.
The reasoning behind this is that r/politics doesn't ban people or articles that the mods disagree with. It's the community itself that downvotes pro-Trump stuff. r/The_Donald, on the other hand, bans people who make comments critical of Trump and people who submit anti-Trump articles. Similarly, r/enoughtrumpspam or r/communism should also be banned from making it to the default front page (I don't know if they actually are).
The reasoning behind this is that r/politics doesn't ban people or articles that the mods disagree with. It's the community itself that downvotes pro-Trump stuff. r/The_Donald, on the other hand, bans people who make comments critical of Trump and people who submit anti-Trump articles. Similarly, r/enoughtrumpspam or r/communism should also be banned from making it to the default front page (I don't know if they actually are).