Twitter has been extremely heavy on censorship this year. Dozens of high-profile users banned, hundreds 'shadow-banned', and unbelievable levels of hashtag manipulation. Twitter is not in favor of free speech, on top of being a terrible business.
Which users were banned for expression of opinions? I initially wrote "high profile", following your comment, but I don't actually care. High profile or not, that would make me worry.
I know Milo was banned based on the accusations that he'd orchestrated harassment of Leslie Jones, but I haven't heard of anyone being banned simply for expressing a political position.
As far as hashtag manipulation goes, I'm not sure what you mean. If you just mean they don't put some hashtags on trending, that may or may not be a bad approach to promoting healthy debate, but it's not a free speech issue.
Look into why Charles Johnson was banned. They took a statement he made that obviously meant "I am going to write a news story about this person that will be very bad for them" and tortured it into a death threat, and banned him for life.
There is literally no defense of this because it was so obviously a bad-faith interpretation, and yet other people have very obviously put people in actual danger, like Spike Jones tweeting George Zimmerman's parents home address, and nothing happened to them. Johnson, whatever you might think of him personally, was banned forever for something he obviously did not even do when you look at the tweet. If they like you, you can say almost anything. If they don't almost anything can get you suspended.
The hashtag trending thing is another case of this, if they basically like your message then they'll let it trend, if they don't then they'll suppress it. You can only really derive that this is happening from observing in very specific ways, no one actually tells you they do this. They have other tricks too, if an undesirable hashtag gains popularity, out of nowhere a misspelled hashtag autocompletes, to "nudge" you to a dead end hastag that nobody is listening to. It's fairly obvious once you become aware of it, because popular hashtags autocomplete, unpopular or not-trending ones don't, but "roach motel" hashtags somehow bypass this. Nobody knows globally what this single corporation decides to let be widely heard and what it invisibly suppresses. It is a free speech issue because private or not, as the Arab Spring stuff demonstrated how much influence Twitter has on society, which makes it one. This is the bog-standard, not-full-of-shit liberal position. It's even Chomsky-endorsed.
1) Interesting that you mention doxxing in the context of Chuck Johnson, since when he was banned for his tweet about Deray, he had already posted home addresses of two NYTimes reporters. That both a) indicates that he was a bad actor, and b) colors how you might interpret comments about "taking out" someone. It doesn't turn it into a threat of violence, but it does make it look a lot more like using Twitter to organize harassment.
The other thing is that this is just a tough way to argue. There's massive amounts of harassment on twitter, and enforcement is incredibly haphazard. Did Spike Lee get a pass because he's a liberal? Or because in 2012, Twitter was completely clueless about any kind of response to harassment?
2) Hashtags: as it stands, everything you've said is your own personal observation and too vague for me to even try and confirm. Rather than repeat myself, let me just reference my other comment about doing the work to prove your accusations: https://news.ycombinator.com/item?id=12936414
3) I will however, repeat my question from before: is there any political opinion that I can utter as an American citizen that will get me banned from Twitter?
1) The Clint Eastwood case seems to be a fake account: http://nypost.com/2016/11/10/clint-eastwoods-twitter-account..., which doesn't entirely answer the question of why it was banned, but definitely muddies the waters. Do you have an example of someone not potentially impersonating a celebrity?
2) The Wikipedia page primarily concerns cases where Twitter is ordered to engage in censorship by other countries, not Twitter choosing to censor opinions on its own . I wish they would tell Ergodan where to stick it, but that's not the same as them posing a threat to your speech or mine (assuming you're not from Turkey).
Let me ask you an unambiguous question. I am a citizen of the United States of America, a country with a strong tradition of freedom of speech. Can you offer me any reason to fear that I am going to be censored by Twitter for expressing an opinion (liberal, conservative, fascist, even)? To be perfectly clear, and avoid confusing matters with the issue of harassment, say that I do not @-mention other users.
Twitter shadowbanned me for posting details of child abuse I experienced that left me disabled. These details included the names of people involved and summaries of acts committed against me. Some of the principals in these acts and all of the accessories to them are employees of a school board, police department, city government, and political boards. I posted links to articles from local media showing that there's a culture of child abuse in the city and that it still pervades more than 25 years after I was abused. I identified a certain juvenile detention facility and explained how it was designed to be and operated as a wholesale child abuse factory. I posted a report from the Department of Justice calling out the state on the ways that it abuses children.
Twitter apparently thinks that trying to effect positive change, to-wit, ending the wide scale child abuse and holding the abusers accountable to law, is a bad thing.
Whatever. Unless it's carefully moderated (ie., censored, to some) it will gather a large collection of angry right-wing posters or angry left-wing posters. One side will harass the other and the other side will eventually go elsewhere. Then it will be just another echo chamber.
If the creator has pivoted to the alt-right, it's a pretty sure guess that it will wind up being another 8chan/stormfront/what have you.
It's the Twitter for free speech.