Trump threatens to 'close' down social media platforms

How can the "private platform so they can do whatever they want" crowd reconcile their views on election interference using social media in 2016 with this latest move by Twitter? If they can do what they want with their platform why did it matter in 2016 and why does it not matter now?

I can't directly answer the question. However, I think what complicates this issue is the political actors involved. Twitter may be a private platform, but when the President posts a Tweet, that is very much a public, political, government message.

For example, a federal judge barred Trump from blocking followers, despite Twitter being a private platform.

https://www.cnbc.com/2018/05/23/trump-cant-block-twitter-fol...

The big difference here is the judge was restricting Trump as a government actor from doing something while the Twitter side of things is Twitter doing something on their own platform. Trump very much was using Twitter as the official place for announcements for a while and if it's the official place to learn government policy you can't block people from seeing it.

What views are you insinuating that I have on "election interference using social media in 2016"?

That's a false equivalence.

Arguing that a platform shouldn't have to host arbitrary content isn't the same as saying that a platform should get to host arbitrary content. If you run a website I'd argue that you shouldn't have to post other peoples' content on it - that doesn't mean I think you should get a free pass to post any illegal content you like - which was the issue with election interference.