I was hosting my own content on Twitter's service, same as I do on my web host.

In both cases, you're not "hosting your own content" by anyone's definition of the term. You're paying someone to host it. Anyway, all web hosts have rules aka terms of service aka censorship.

It's my right (and Twitter's) to offer a service that has terms, and those terms can include removal of speech that I feel is bad for my business. This is a basic freedom of association -- I don't have to do business with people whose speech I don't like, and I certainly don't have to broadcast it.

Arguing that Twitter must be a neutral host is like arguing that Uber or Airbnb can't ban customers for saying racist things (both have) or that Facebook must accept 100% of ads.

If you are conveying someone's speech as a service as part of a for-profit, private business, you can choose not to convey that person's speech for any reason. There is no demand in the US (Constitutional, statutory, or otherwise) that a private entity broadcast the speech of another entity. In fact, that's a violation of the broadcaster's First Amendment rights (as repeatedly upheld by liberal and conservative justices, over and over again).