As someone who follows /r/ShitRedditSays and /r/SubredditDrama on and off I find it completely unsurprising. For years reddit has been fertile recruiting ground for racists, sexists, anti-semites, homophobes, transmisogynists, and ableists. This is largely the fault of Reddit's administrators who had a strict laissez-faire approach to content on their site and refused to remove content that was overtly any or all of the above. Hell, getting them to remove /r/jailbait (which, even if the public posts were strictly legal (a few posts were proved not), provided a convenient meeting place for actual pedophiles who would trade illegal content over private messages) required the attention of the mainstream media! In 2015 they created a Terms of Service that bans "involuntary pornography" and content which "encourages or incites violence" or which "threatens, harasses, or bullies" but before then they did not.
The admin's attitude towards speech on their site fostered a strong contingent of posters who posted edgy "ironic" non-politically correct content in what was a relatively safe space to do so. Having a place where this type of speech was normalized attracted people who actually believed those non-PC stances and they posted "ironically" as well until the lines between irony and un-irony completely broke down. A very good example of this is /r/fatpeoplehate. Before it was banned it was one of the fastest-growing subs and their horrible bullying "memes" permeated the site ("found the fattie!"). After it was banned there was a brief shitstorm in which FPH subscribers flooded the site with FPH content but after a few weeks they largely disappeared from the site. Fortunately FPH was nipped in the bud; other hate/bullying groups are established enough on the site that even the removal of their dedicated subs (like the Chimpire network) did/will not drive them off.
You may have also been under the impression that Reddit in general (as much as that can be a thing) was somehow "progressive." This has some truth to it but the events of the past few years have mostly exposed this for what it mostly really was: "brogressiveism." Basically, on any issue that would impact young white middle-class men Reddit will generally hold progressive views. This includes gay marriage, drug legalization, college tuition/student debt, etc. But when it comes to issues that do not affect that demographic Reddit becomes far more conservative. The blistering responses to Black Lives Matter (about racial inequality) and Tropes vs. Women/GamerGate (about feminism and representation in video games) demonstrate this nicely. (That's not to say there are not people who are genuine progressives on Reddit; there most definitely are but they are far outnumbered by "brogressives" and outright conservatives on the most popular subs.)
/r/The_Donald combines both of these traits. It may have started ironically as a way for people to make jokes about a joke candidate, but just as his campaign became serious so too did the "jokes" on /r/The_Donald. Additionally, Donald Trump has enough brogressive views that he can appeal to that crowd without the inconvenience of challenging them to consider people who have different life experiences than their own like true progressive candidates would. Basically, /r/The_Donald is a perfect confluence of issues that have been underlying Reddit for years.
You mean they allowed speech that didn't tread on the rights of others? I think racism is shitty too, but I'm not going to ban it. And that makes me sound like a bad person, but people's definitions of racism vary extremely widely.
It's not possible to say something without offending someone out there. If you think taking down posts that simply offend you is a good idea (rather than ignoring posts that you don't like and refusing to take those people seriously), then there are other platforms out there.
Better yet, you can make your own subreddit and stop complaining about the others on the site.
Everyone else has as much a right to reddit as you do.
> brogressive
Libertarian?
There's nothing wrong with having a differing opinion.
> blistering responses to BLM [...] demonstrate [conservatism] nicely
So you're saying that people who disagree with BLM in some way are conservative?
I disagree with their methods. Am I a conservative now?
> BLM, GamerGate, Trump supporters
Do you think these groups should not be allowed to use reddit?
You are right that at some point what is and is not acceptable speech becomes a judgement call but at the same time some speech is so incredibly corrosive to the health of a community that you must draw that line. All social media sites should be taking that lesson from Reddit.
"If you don't like the moderation just start your own sub" is a nice idea but breaks down in practice. The very reason you visit Reddit is to discover and discuss links. If you don't like how a sub is moderated you can start your own but that doesn't mean anyone else will use it over the other one. If there is a general sub for topic X just starting a sub that is "X with stricter moderation" isn't very likely to attract a lot of users. However, if you frame it as "X for people [pro/anti]-hate" you are going to draw in the passionate minorities of users on either side which will cause extremification rather than moderation. Having an extreme sub may also attract users who are only marginally interested in X but have a deep interest in the hate (for or against) which will cause further extremification.
This extremification can in turn poison the general subs. On Reddit if a link is posted in multiple subs there will be an "other discussions" link which will show you where else that link has been posted. If a news story is posted in both a general sub and a [pro/anti]-hate sub the users from the latter can easily find and post/vote on the general sub's discussion. (Not to mention posting Google-able quotes and outright direct links to other subs.) This was overtly a major problem with /r/fatpeoplehate. If a link (or quote or screenshot) was cross-posted to FPH you could count on FPH trolls to show up in short order and flood the general discussion with their hate. Even when it's not that overt the extreme users can subtly shift the tone of a general sub towards their point of view over time, such as with rampant racism on /r/worldnews.
The most straightforward solution to this that I can see is to 1) moderate general subs so that their tone remains, well, moderate, and 2) ban extremely offensive subs (using the standards of society at large as an indicator of what is too extreme). That's not to say this is an easy task or even clear-cut in many cases and it will prevent some people from expressing their legitimate opinions, but if the thin extremes at the end of the bell curve need to be cut for the benefit of the fat middle on a privately-controlled website I do not see a problem with that. (I do believe that governments should not restrict speech but social media sites are not governments and should not be held to the same standards.)
EDIT: Also, to clarify, the third paragraph of my original post was regarding people's perceptions of Reddit in aggregate, not how it actually is. Reddit (for a time) had a reputation as "progressive" but the reality does not and did not not match this reputation. I did not intend it as an attack on people who have non-progressive views (I obviously consider myself a progressive), I was merely providing examples of how the reality of Reddit's aggregate political views (to the extent that millions of people can be classified as having aggregate political views) are (or can be perceived as) "progressive" on some prominent issues but non-progressive/conservative on others.